air conditioning diagnosis service and repair v2

Air Conditioning Diagnosis,

Service & Repair

Copyright 2011 Standard Motor Products, Inc. All Rights reserved.

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Portions of this manual COPYRIGHT 2011 Standard Motor Products, Inc. The material herein, may not be used without the prior express written permission of the copyright holder, including, but not limited to reproduction or transmission in any form by any means such as electronic, mechanical, photocopying, recording or otherwise; nor may it be stored on any retrieval system of any nature. DISCLAIMER OF WARRANTIES: Although the information contained within this volume has been obtained from sources generally believed to be reliable, no warranty (expressed or implied) can be made as to its accuracy or completeness, nor is any responsibility assumed by Standard Motor Products, Inc. for loss or damages suffered through reliance on any information contained in this volume. SPECIFICALLY, NO WARRANTY OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE OR ANY OTHER WARRANTY IS MADE OR TO BE IMPLIED WITH RESPECT TO THIS VOLUME AND ITS CONTENTS. In no event will Standard Motor Products, Inc. be liable for any damages, direct or indirect, consequential or compensatory, including, without limitation, lost profits, for any representations, breaches or defaults arising out of the use of this volume. Customer agrees to indemnify Standard Motor Products, Inc. and hold it harmless against all claims and damages, including without limitation, reasonable attorneys fees arising out of the use of this volume, unless such claims or damages result from the infringement of any copyright or other proprietary right of any third party.


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TABLE OF CONTENTS Introduction 5

Service Precautions 6

New Technologies R-1234yf (HFO-1234yf) 8

R744 (CO2) 9

SAE J2788 Recovery/Recycling/Recharging Equipment 12

Leak Detectors 13

Clutchless Compressors 14

Stretch To Fit Belts 16

Hybrid Vehicle Service 17

Service Tips Condenser Restriction Check 20

Belt and Tensioner Service 21

Ford Scroll Compressor Issue 21

Ford E Van Clutch Circuit Issues 22

Ford Diesel Van Compressor Issue 23

GM Vehicles In-the-Line Filter 24

Saturn Rotary Vane Compressor Issue 25

Orifice Tube/TXV Dual Evaporator System Issues 26

GM Compressor Failure 27

Honda CRV Compressor Failure 27

Honda Condenser Issue 28

Honda CRV AC Performance Issue 28

Dodge Truck AC Clutch Issue 28


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TABLE OF CONTENTS continued Service Procedures Compressor Replacement Steps 29

Lubrication 32

Compressor Oil Chart 33

Refrigerant Recovery, Recycling and Recharging 34

Recovery 35

Evacuation 39

System Charging 41

Flushing 43

Leak Detection 46

Trace Gas Leak Checking 50

Case Studies Case Study #1. 1998 Jeep Wrangler Compressor Failure 50

Case Study #2. 2001 Ford F150 Poor Performance In Stop/Go Traffic 55

Case Study #3. 2001 Chevy Tahoe Rear AC Issue 59

Reference Material Temperature Testing 63

Temperature Testing Flow Charts A, B and C 72

Determining TXV System Charge Level 75

VDOT System Testing 79

Temperature/Pressure/Humidity/Micron Vacuum/Altitude etc - Charts and Worksheets 92


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INTRODUCTION

This class is designed to help you, the air-conditioning technician, diagnose and repair the refrigeration circuit on most automotive AC systems using a variety of techniques including Maximum Heat Load Temperature Testing. The course covers new HVAC technologies such as electronic variable displacement compressors and a replacement refrigerant for R134a, best practice AC service procedures, service tips and pattern failures. It also has several case studies that illustrate common AC service issues and how to avoid them. We do not focus on a particular manufacturer. The case studies are chosen because they illustrate common failures or service missteps to be avoided. The March of Technology and Its Impact on Air Conditioning Service and Repair New HVAC technologies are constantly being introduced that make servicing air-conditioning systems an ever more exacting science. Successful air-conditioning repair today requires attention to every detail of the repair recovery, evacuation, refrigerant handling, refrigerant and oil charge accuracy, system flushing etc. Manufacturers face three distinct pressures driving them to find ways to improve the efficiency of air conditioning systems. Essentially this means getting the same job done with less less refrigerant, less oil, less fuel, less materials (lighter). As you can imagine, when you try to accomplish more with less, every component in the system must perform at maximum efficiency all the time. This means that when it comes to repairing these finely balanced systems, there is simply no margin for error at any step in the repair process. Here is a brief summary of some the pressures driving manufacturers to constantly fine tune and improve HVAC technology:

Because R134a is believed to cause global warming, manufacturers strive to make every component in the AC system more efficient in order to use as little of the refrigerant as possible; for example, by improving the heat exchange efficiency of the condenser and evaporator.

There is a continuing incentive to improve CAFE fuel economy standards. Air-conditioning is typically the largest single accessory load on the vehicle any AC efficiency gain is indirectly a fuel economy gain.

Global warming again burning fuel produces CO2, a green house gas. Manufactures receive specific AC credits from the EPA for any technological AC system improvement that reduces direct refrigerant emissions or reduces tail pipe (CO2) emissions. Therefore, any technology that improves AC efficiency indirectly reduces CO2 production. Examples of this type of technology are:

o Reduced reheat with the use of electronic variable displacement compressors o Oil separators to reduce the amount of oil circulating in the system - oil coats heat

exchange surfaces reducing their efficiency. o Default to recirculate when possible, to reduce wasted energy o Use of internal heat exchangers


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o Ever smaller condenser tubes and complicated internal refrigerant routing. o Electronic expansion valves. o Greatly reduced system refrigerant and oil capacities o The Ejector Cycle evaporator (Toyota).

Note: The greenhouse gas (GHG) effect of the CO2 produced by the extra fuel burned to drive the air conditioning load is much greater than the GHG effect caused by the release of the refrigerant itself into the atmosphere. Service Precautions Before proceeding with system diagnosis, the following precautions should be observed:

Ensure that AC system pressure is released before opening the AC system at any point. The AC system is under pressure and may cause personal injury.

When using a jumper wire, ensure either the jumper wire or circuit is fuse-protected. Disconnect the battery cable before disconnecting a connector from any control module. DO NOT cause short circuits when performing electrical tests. This may set additional

Diagnostic Trouble Codes (DTCs), making diagnosis of original problem more difficult. You could also severely damage or destroy electrical and electronic systems and components.

Use specified test equipment when performing electrical tests. Follow OE manufactures specific safety procedures and directions when working on high

voltage (HV) hybrid vehicles. Be sure you have the right equipment for handling and testing HV systems.


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NEW HVAV TECHNOLOGIES AND STANDARDS

Alternative Refrigerants The Future of R134a The refrigerant R12 is believed to have two detrimental environmental effects:

1. R12 depletes the ozone layer which prevents harmful Ultraviolet (UV) light from reaching the earth.

2. R12 contributes to global warming by acting as a Green House Gas (GHG). R12 has a global warming potential (GWP) of about 8100.

The introduction of R134a in the mid 1990s eliminated the problem of ozone depletion from this source but did not completely eliminate the issue of global warming. R134a, although not an ozone depleter, is also believed to contribute to global warming. Its GWP is calculated at about 1400. For this reason, the European Union has banned the use of any refrigerant with a GWP of more than 150 in all new vehicle platform models after 2011 and in all new vehicles produced after 2017. This means of course that R134a with its GWP of 1400 must be phased out in Europe over the next several years. At this time, the use of R134a in the U.S has not been banned (see note later on states regulation of R134a). However, to reduce production costs, OE new car manufactures would prefer to use just one global refrigerant. It is likely therefore that the changes taking place in Europe will be felt in the U.S. At least some of the vehicles you will work on in the next several years will almost certainly use a refrigerant other than R134a. The refrigerant HFO-1234yf was approved in early 2011 under the EPAs Significant New Alternatives Policy (SNAP) program for approving non-ozone depleting refrigerants. It is now legal to use subject to the EPAs Acceptable Subject to Use Conditions. This means unique vehicle service ports, labeling etc are required. HFO-1234yf will be known in the industry as R-1234yf. See the notes on the following pages on R-1234yf and R744. Refrigerant and automobile manufacturers have been searching for a suitable replacement for R134a for several years. A number of alternatives have been proposed but none has met all the demands that would be required of an acceptable alternative refrigerant. To meet international regulatory requirements and be acceptable to car manufacturers, an acceptable alternative refrigerant would need to meet the following criteria:

Have no ozone depleting potential Have a global warming potential of less than 150 Be non-toxic chemically safe.

Have low flammability Be reasonably compatible with existing HVAC technology in other words have a similar

pressure/temperature and performance profile to R134a Be an effective refrigerant

Believe it or not, it has been extremely difficult to develop a chemical that meets all these requirements completely. However, a new refrigerant, R-1234yf, has now been developed which does in fact meet these criteria. It is now very likely to become the global replacement for R134a in new vehicles over the next several years.


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R-1234yf (HFO-1234yf) R-1234yf is a joint development of the Honeywell and DuPont chemical corporations. It has a GWP value of only 4 compared to about1400 for R134a. Its temperature, pressure and performance characteristics are very similar to R134a (see graph). It boils at -22.3F versus -14.8F for R134a. Evaporator pressure for a temperature of 32F is 31.4 PSI compared to 27.8 PSI for R134a. The American Society of Heating, Refrigerating and Air-Conditioning Engineers (ASHRAE) have given it an A2L classification, which means mildly flammable. Extensive tests have shown it to be quite safe in normal service circumstances. Functionally, these characteristics make it a near drop in replacement for R134a. However, the flammability issue will have some impact on system design, service equipment and technician training - primarily from a safety perspective. Refer to the section later on the many new SAE J specifications being developed to address the introduction of the new refrigerant. For example, evaporators intended for use with R-1234yf must meet SAE J2842.

Lubrication and R-1234yf It is expected that most systems will use a PAG oil similar to existing PAGs but with a special additive package specific to R-1234yf. R-1234yf is chemically less stable than R134a and it is harder to maintain oil miscibility in the system.

50/50 Mix R-1234yf & R134a

F

PSI

R134a

R-1234yf

R-1234yf/R134a Pressure Temperature Relationship


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R-1234yf Service Equipment All new service equipment will be required including recovery/recycling/recharging equipment (SAE J284), refrigerant identifiers (SAE J2912) and leak detectors (SAE J2913). Overall, however, because of the basic similarities between the two refrigerants, equipment and service procedures will be similar to working with R134a. Vehicles will have all new high and low side service ports. Recovery and recycling of R-1234yf will be required.

R-1234yf New Tank A new tank of R-1234yf will be white with a red band toward the top.

R744 (CO2) CO2 has been proposed as an alternative to R134a for a number of years. The refrigerant itself is very acceptable from an environmental perspective it does not affect the ozone layer and has a GWP value of only one. However, CO2 is not as efficient as R-1234yf (or R134a) as a refrigerant. This means more energy is required to drive the system to produce the same level of cooling. This reduces fuel economy and drives up GHG tailpipe emissions of CO2! Another drawback of CO2 is that its pressure/temperature profile is vastly different from R134a. The static pressure in a CO2 system with the engine off on a summer day is around 900 PSI! High side operating pressure could be as high as 2500 PSI. Therefore, CO2 requires radically different (and expensive) system components than R134a. CO2 would require significant on-vehicle safety systems to handle an accidental venting of the gas inside the passenger compartment. Naturally, service equipment and procedures would be also very different. For a while, some European manufacturers appeared committed to CO2. However, at this stage, it appears unlikely that any OE manufacturers will adopt the use of CO2 in their vehicles. The majority of automobile manufacturers favor the use of R-1234yf. R744 (CO2) is however still likely to be approved as a legal refrigerant under the EPAs SNAP program.

New Vehicle Refrigerant Decal Vehicles with R-1234yf will have a new underhood air-conditioning system decal. It will include the following information:

New R-1234yf Tank Will be White with a Red Band


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Safety warnings The refrigerant type and capacity. Oil type

SAE J639 certifies that the system meets safety standards for Motor Vehicle Refrigerant Vapor Compression Systems.

J2842 - certifies that the evaporator meets safety standards for use in an R-1234yf system. J2845 Indicates that the system should only be serviced by certified personnel trained in the

Safe Service and Containment of Refrigerants. R-1234yf Evaporators J2842 is a new SAE design and certification standard, for evaporators intended for use with R-1234yf or CO2. The new specification was developed because of the flammability risk (mild) associated with R-1234yf and the high pressures and possible poisoning in the event of an in-cabin release of CO2. J2842 evaporators must carry a label that indicates that that they must be discarded if removed from the vehicle for any reason and that they should only be serviced by certified personnel. Replacing a J2842 evaporator with a junkyard unit would not be permitted. R-1234yf Recovery/Recharging/Recycling Equipment SAE J284 is a specification for recovery/recycling/recharging equipment for servicing R-1234yf systems. Here are some of the features of J2843 equipment:

Arc resistant switches.

Special ventilation since R-1234yf is flammable (mildly). Leak testing capability - the machine must perform both a vacuum and a pressure leak check

during evacuation and charging respectively. o Vacuum leak test - hold a steady vacuum for two minutes after evacuation. o Pressure leak test - the machine charges 10% of the system charge and monitors for

pressure decay before completing the charging cycle. The machine will halt the charging cycle if the system fails this test.

o The equipment must have a built in refrigerant identification capability to prevent accidental cross contamination of refrigerants.

Note: The issue of refrigerant identification may become an issue later. As R-1234yf vehicles become more common, the possibility of cross-contaminated R-1234yf and R134a is likely. The static pressure in a tank of R-1234yf/R134a cross contaminated recovered refrigerant will be slightly higher than in a tank of either refrigerant on its own. This could result in the auto air-purge function of the

Type of Refrigerant R-1234yf or CO2 Manufacturers

Logo

New SAE J2842 Decal for Evaporators


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recovery/recycling equipment (for either refrigerant) bleeding off the entire tank of recovered refrigerant. Retrofitting and R-1234yf At this time, there are no plans to retrofit older vehicles with R-1234yf because of the flammability concern. R134a will continue to be available to service vehicles that use it. More SAE J Standards

Most of the following SAE standards relate to the introduction of R-1234yf :

J639. This is a broad safety design standard for motor vehicle Refrigerant Vapor Compression Systems. It has been recently revised to include standards for R-1234yf.

J2845. This standard details the training requirements for technicians working on R-1234yf and CO2 systems especially as it relates to safety and refrigerant handling.

J2099. This is a refrigerant purity standard for recycled R-134a and R-1234yf.

J2297. This is a stability and compatibility standard for fluorescent refrigerant leak detection dyes for R-134a and R-1234yf systems using ultraviolet leak detection.

J2911. This is a broad industry standard certifying that required SAE J standards for mobile air-conditioning system components, service equipment, and service technicians have been met. It provides assurance to regulators and customers that equipment, etc delivers advertised performance.

J2670. Stability and compatibility criteria for additives and flushing materials intended for aftermarket use in R-134a and R-1234yf systems.

J2762. This standard certifies a method for removal of refrigerant from an air conditioning system to quantify the charge amount.

J2842. This is a new design and certification standard for R-1234yf and CO2 evaporators described earlier.

J2843. New standard for recovery/recycling/recharging equipment details described earlier.

J2851. Similar to J2843 but for recovery only equipment.

J2912. New performance criteria for R-134a and R-1234yf refrigerant identifiers.

J2913. New performance criteria for R-1234yf electronic leak detectors.

J2927. A standard for refrigerant identifiers installed in R-1234yf Recovery/Recharging/Recycling machines.


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SAE Standards for R134a Service Equipment

SAE J2788 Recovery/Recycling/Recharging Machines SAE J2788 is the current standard for R134a Recovery/Recharging/Recycling equipment. The standard was introduced several years ago for a number of reasons. Several studies indicated that older equipment could leave as much as 30% of the old refrigerant in the system during a typical recovery procedure. If the service process was short-circuited by going straight from recovery to recharge (without evacuation) then the potential for a serious overcharge was high. On top of this, the continuing trend toward ever-smaller system charge capacities meant there was less room for even small errors in refrigerant charging amounts. System capacities of 12 to 16 ounces are common. An error of just an ounce or two in either direction can result in catastrophic compressor damage and system performance issues. Today, exact system charge level is critical for successful AC service. Machines manufactured to meet J2788 ensure much more complete recovery of refrigerant. They also ensure much more accurate metering of the exact charge amount. Compliant machines must recover at least 95% of the refrigerant in 30 minutes. J2788 machines have a charge tolerance of +/- 0.5oz. Older machines were significantly less accurate. An undercharged system can cause poor compressor lubrication and catastrophic failure and of course poor performance. An overcharged system can cause liquid slugging of the compressor and compressor damage, high system pressures, high vent temperatures and compressor cut-out switch activation. J2788H The H suffix denotes hybrid. This is a specification for recovery machines intended for use on hybrid vehicles that use a High Voltage (HV) electric compressor. The idea is to prevent oil cross contamination between conventional AC systems that use PAG oils and HV compressors that use an ester based oil. Ester based oil is used in HV systems because of its superior dielectric properties over PAG. If even a small amount of PAG (as little as 1%) were to contaminate a HV system, a high voltage leak could occur. This can result in a complete vehicle shut down and severe damage to the system. Refer to the Hybrid section below for more information on this issue. Typically, these machines come with an adapter that enables liquid refrigerant to be circulated through the service hoses to flush any traces of PAG oil before servicing a high voltage system.

J2788 & J2788H Compliant Recovery/Recharging/Recycling Machine


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J2791 and J2913 Electronic Leak Detectors Because of reduced charge capacities, even a small leak can result in a performance issue and possible compressor damage much more quickly than the same leak on a larger capacity system. The need to detect ever-smaller leaks has become much more critical. In response to the need for more reliable and accurate leak detection, SAE International published J2791 for R134a electronic refrigerant leak detectors several years ago. J2791 leak detectors can find leaks as small as .14 oz/year (4 grams) per joint. The old standard was .5 oz (14 grams). They are also less sensitive to false triggering and are more robust. Note SAE has now issued a new standard, J2913 for R1234yf leak detectors. Detectors meeting this standard must be able to differentiate between a 4, 7 and 14 gram leak (approximately 0.141, 0.247 and 0.5oz). Some detectors meet both J2791 and J2913 standards. State Regulations R134a California (and possibly other states) is proposing to introduce their own restrictions on the use of R134a similar to those underway in Europe. Their proposal would likely require the use of a low GWP refrigerant in new vehicles. Wisconsin has had a law in place since October 1994 prohibiting sales of container sizes holding less than 15 lbs of R134a. However, this restriction applies only when the chemical is intended to be used as a refrigerant. For example, it is legal for a person to purchase gas duster containers with any amount of the chemical because in that instance, the chemical is neither intended to be a refrigerant nor is HFC-134a included in the listing of Class I and Class II substances.

J2791 Electronic Leak Detector for R134a

Refrigerant Combination J2913

and J2791 Leak Detector Detects R134a & R1234yf


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Electronic Variable Displacement Clutchless Compressors In the past several years, a number of manufacturers have started using a new computer-controlled compressor. This design of compressor is gradually becoming standard on many vehicles. Chrysler/Jeep, GM, Toyota, Nissan, ME/BE, Audi/VW and Kia have used it on different models. The basic design is similar to a conventional wobble plate variable displacement compressor. The key differences are:

1. To control compressor displacement, they use a pulse width modulated solenoid, controlled by the computer. This solenoid replaces the conventional control valve that responds to suction line pressure. The computer varies the duty cycle command to the solenoid to route more or less pressure to the rear of the pistons to change the angle of the wobble plate. In this way, the pumping capacity of the compressor can be varied from almost zero to maximum capacity (1% - 100%).

The computer takes account of a range of inputs to decide the appropriate compressor displacement. It can optimize the system for best air-conditioning, fuel economy and engine performance. Depending on the system design, it can monitor evaporator case temperature, system pressures, ambient and cabin temperatures, driver inputs etc.

When the Wobble Plate Is at an Angle to the Shaft, the Piston Stroke Is at Maximum

Maximum Stroke

When the Wobble Plate Is at Right Angles to the Shaft, the Piston Stroke Is Almost Zero

Piston Stroke Reduced to Zero

Variable Displacement Control Solenoid

Electronic Variable Displacement Compressor

Electronic Control Valve

No Clutch


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2. There is no electric clutch the compressor shaft turns all the time when the engine is running, even with the AC off. Lubrication is especially critical. Note: The system must be properly charged with refrigerant and oil at all times to maintain adequate lubrication These compressors are designed to keep more of the oil charge circulating within the unit to maintain lubrication even when the AC is off. The compressor pulley contains a damper to absorb engine torque fluctuations and a limiter mechanism that allows the spoke portion of the pulley to break away in the event that the compressor locks up. This allows the compressor pulley and any other accessories driven by the same belt to continue to turn.

Electronic Variable Displacement - Compressor Control The computer varies the duty cycle command to the compressor control solenoid to match the heat load on the system. When the heat load is high, the computer increases the On command to the solenoid. The oscilloscope patterns shown here illustrate the command to the solenoid at idle on a 2008 Dodge Caliber during both low and high heat load conditions. The solenoid is permanently grounded and is positive pulsed by the computer.

Quick Tip:

The computer is in complete command of the compressor pumping displacement. If you find that the compressor does not appear to be building pressure, even after evacuating and recharging the system, do not immediately condemn it. The computer may not be sending the correct signal to the solenoid.

Solenoid + Duty Cycle = 87%

Solenoid Current = 0.8A

High Heat Load Greater Duty Cycle Command to Solenoid (87%). Solenoid Current = 0.8A

Solenoid + Duty Cycle = 43%

Solenoid Current = 0.4A

Low/Medium Heat Load Medium Duty Cycle Command to Solenoid (43%). Solenoid Current = 0.4A


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For example, if the solenoid is unplugged, the compressor defaults to minimum displacement about 1% of capacity. Check for HVAC and engine management system trouble codes that might be inhibiting AC operation. Check also for inaccurate sensor inputs that might cause the computer to send the incorrect command to the solenoid e.g. inaccurate system pressure sensors, inaccurate evaporator or ambient/cabin temperature sensor readings. Stretch to Fit Belts General Motors started using Stretch to Fit Belts on the 2008 Hummer H3 and 2009 full sized trucks: Silverado, Avalanche, Tahoe, Suburban, Express Van, Sierra and Yukon. They are also used on midsized pickups and SUVs such as the Colorado, Trailblazer, Canyon and Envoy and on Saab 9-7 and Cadillac CTS-V. Ford uses stretch to fit belts for the power steering on 2008 and up Edge, MKX, Fusion, Milan MKZ and MKS with 3.5/3.7L engines. Chrysler uses stretchy belts on the power steering pump of 2007 and up 2.7L engines. The belt is very similar in appearance to a conventional serpentine belt. However, the reinforcing cord is made of a polyamide material which is more elastic than the aramid or polyester cord used in traditional belts. The Polyamide cord, when combined with a more elastic backing compound, gives the belt it's stretch quality. As a result, the belt is able to maintain proper tension throughout its life without the use of a tensioner. Note: GM states that once the engine is operated with the stretch belt installed, the belt cannot be removed and reused. It is designed to be removed by cutting it off. Ford and Chrysler indicate that the belts can be reused provided special tools are used to remove and reinstall the belts.

Removing Stretch to Fit Belt on GM Vehicles

Using Special Tool to Install Stretch to Fit Belt on GM Vehicles Several Manufacturers Make a Tool for This Purpose

Belt Installation Tool

Belt Installation Tool


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Hybrid Vehicle AC Service Safety: Servicing hybrid air-conditioning systems requires special precautions over and above normal AC service. There are many flavors of hybrid vehicles using a range of voltages from 42 to almost 400 volts. Many use high voltage to drive an all-electric compressor. High voltage (HV) can be lethal. Each manufacturer has specific safety procedures that must be followed when working on their particular HV vehicle. Working on hybrid vehicles requires special attention in three main areas:

1. Servicing HV system or components this includes working on the HV compressor used on many Hybrids. Hybrid vehicles have HV disconnect plugs or switches to disable the HV system. Always follow the specific procedures for making the HV system safe to work on. When working on a HV system you will need some dedicated safety gear and equipment. Always wear a pair of HV class 0, 1000 volt rubber gloves. Electrical system checks should be made using a CAT III rated DMM. The meter leads must also be rated for 1000V.

2. Idle Stop System. The gasoline engine may not always be running on a hybrid vehicle. It can start up unexpectedly any time the system is on. To avoid potential injury or damage, always follow the OE manufactures procedures to prevent unexpected gas engine start-up while working on the vehicle.

3. HV Compressor Lubrication. HV compressors use a special formula polyolester (POE) oil. POE oil is used because of its high dielectric qualities. The motor windings of high voltage compressors are exposed to the refrigerant and oil. Extra care must be taken to avoid any contamination entering these systems. If the oil becomes contaminated, high voltage can find a path to ground through the oil. The vehicle management system will set high voltage leakage codes and may completely disable the vehicle - it might not start at all. Repairing the vehicle may require replacing every component in the refrigerant path compressor, condenser, evaporator etc.

Note: Just 1% of PAG contamination in the POE oil A Bright Orange Cable Connected to the

Compressor Indicates High Voltage

Toyota Prius

CAT III DMM

Class 0, 1000V Rubber Safety Gloves


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in a hybrid system can compromise the dielectric strength of the POE oil. PAG oil residue from the service hoses of your equipment could allow this to happen. You should only use Recovery/Recycling/Recharging equipment meeting SAE specification J2788H - the H suffix stands for hybrid. This equipment is designed to avoid hybrid HV AC system contamination. See page 12 for more detail on these machines. Use a separate, dedicated oil injector to install the POE oil into a HV system (unless your equipment manufacturer expressly states that their machine can handle this task). However, once you know the proper procedures for working with the high voltage system and take care to avoid oil cross contamination, then working on hybrid HV air-conditioning is much the same as working on conventional air-conditioning. Outside of the electric compressor, most of the other components in the system are conventional. Components can be replaced and the system serviced using conventional tools and techniques. Note: Some Honda Hybrid vehicles use a combination belt driven and high voltage electric motor driven compressor. The front half of the compressor is a belt driven scroll and accounts for about 85% of the compressor pumping capacity. The rear half is a brushless electric motor driven scroll. It accounts for about 15% of the compressors capacity. During idle-stop operation, when the gas engine shuts off, the small electric motor scroll can provide temporary air-conditioning assist. The point is that just because you see a belt, dont assume that it is a low voltage compressor. Caution: Even after following the high voltage disable procedure use a Cat III DMM while wearing HV gloves to check that there is no voltage present at the system or component you are about to work on. About Hybrid Compressors Hybrid vehicles may use one of three basic compressor types:

1. A conventional 12V, belt driven compressor with a clutch, similar to a normal AC system. 2. A high voltage AC or DC compressor. These compressors are driven by the same high voltage

used for the vehicle propulsion system. They are easily identified by the bright orange cables attached to the compressor. They do not have a belt and may run when the gas engine is off.

15% Pumping Capacity

Belt Driven Scroll

HV Electric Motor Scroll

85%Pumping Capacity

Suction Discharge

Honda Combination Belt and Electric Motor Driven Scroll Compressor


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3. A combination belt driven and high voltage compressor (used on some Hondas) as described above.


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SERVICE TIPS AND PATTERN FAILURES

Quick Restricted Condenser Check. Many later model vehicles use a high side pressure transducer. The transducer is usually located on the compressor discharge line while the high side service port is located on the liquid line. By comparing high side pressure indicated on the scan tool (discharge pressure) versus gauge pressure (liquid line pressure), you can get some indication if the condenser is restricted. Note that some pressure drop across the condenser is normal. Actual normal pressure drop depends on several factors, including heat load on the system, system design, etc. You will need to gain some experience using the technique by checking known good vehicles regularly.

Read Liquid Line Pressure on Gauge Set

Condenser Restriction Check Compare Discharge Pressure on Scan Tool to Liquid Line Pressure on Gauge Note: Some Drop Is Normal

Read Discharge Pressure on Scan Tool

Pressure Transducer

High Side Service Port


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Belt and Tensioner Service

Typically, the air-conditioning compressor is the largest single accessory load on the vehicle. Each component in the accessory belt drive system (ABDS) must be in good condition to ensure smooth compressor operation. The belt tensioner performs two distinct functions:

Maintain correct tension on the drive belt Dampens torque fluctuations in the ABDS system

caused by the engine firing, the compressor and other accessory loads.

The tensioner can fail in several ways: the spring may lose tension causing belt slippage, wear and squealing. The damper can fail causing excessive belt slap and vibration. The pivot bushing and/or pulley bearing can fail causing uneven belt wear and alignment issues. The circumstances leading up to compressor failure often put the tensioner under excessive strain. AC head pressure may be very high causing the tensioner/damper assembly to bottom out repeatedly and fail. When the compressor is replaced, a belt slippage or vibration problem can be attributed to the replacement compressor when in fact the problem is due to the failed tensioner assembly. A careful check of the tensioner, the belt and other ABDS components should therefore be performed. The alternator and fan clutch are also substantial loads on the system. Their operation should also be checked. Note: Most modern belts are made from an EPDM material which may not show classic signs of belt failure such as cracking. The friction surface may look OK yet be badly worn.

ABDS Quick Tip

Diagnosing ABDS squealing/chirping noise: with the engine running, use a water spray bottle to spritz the underside of the drive belt. If the noise gets worse, it is probably a belt tension issue; if the noise is reduced, it is probably an alignment issue in the ABDS. Ford Variable Displacement Scroll Compressor Issue 2005 2007 Ford Five Hundred, Freestar and Montego models use a variable displacement scroll compressor. The compressor capacity can be infinitely varied between 30% and 100% of output. Variable displacement is achieved with a spool type control valve, with an integral bellows. The bellows expands and contracts in response to suction line temperature/pressure. This moves the control valve back and forth. As the valve moves, more or less refrigerant is allowed to recirculate inside the compressor to vary output. The control valve bellows can fail resulting in reduced

Ford Scroll Compressor Control Valve Can Fail

Causing Reduced Output

The Compressor Is the Largest Accessory Load ABDS Must be in

Good Condition to Drive It

Belt Tensioner: Check Spring Tension, Damper Function, Pivot Bushing

& Bearing Wear


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compressor output. High side pressure will be low and low side pressures will be high with poor performance. The compressor is sensitive to minute amounts of contamination that can cause the valve to stick important to keep in mind when flushing. Ford E Vans - Mid 1990s - 2004 Air-conditioning and Drivability Issues Depending on the time of year, the customer may complain of some or all of the following symptoms:

No AC operation Poor defrost function Surging idle Repeat AC clutch failure

If the problem occurs during the winter, the symptom is usually a surging idle or poor defrost function. During the summer, the symptom is usually no AC operation. Refer to the wiring diagram on this page. Note that the AC clutch voltage must cross four switches before reaching the clutch. Note also that three of the switches would be cycled frequently during normal use: the ignition switch, the AC mode switch and the clutch pressure-cycling switch. With so many active switches in series, the potential for a substantial cumulative voltage drop in the circuit is high. If the AC cycling pressure switch starts to fail, several symptoms can occur.

As the voltage drop across the failing switch contacts increases, the available voltage at the clutch decreases. Eventually the clutch starts to slip, burns up, and finally fails. It may also take out the compressor due to warping of the compressor case or failure of the front seal from the excessive

AC Clutch

Function Selector Switch

AC Clutch Cycling Pressure Switch

PCM

Hot In Run

AC Pressure Cutout Switch

Clutch Diode

AC Clutch Circuit Has Four Switches in Series Increased Likelihood of Large Voltage Drop


23

heat generated by the slipping clutch. If the clutch or the compressor are replaced without the underlying cause of the original failure being identified a repeat failure is likely to occur.

When the voltage drop across the cycling switch becomes so great that there is not enough current to engage the clutch, then another unusual symptom can occur. When the AC (or defrost) is first turned on, current starts to build in the clutch circuit. However, the failing cycling clutch switch contacts are not able to carry the rising current and the switch goes open almost instantly. The clutch never actually engages.

Note from the wiring schematic, that there is a splice off the AC clutch circuit after the cycling switch that goes to terminal 41 at the PCM. This is the AC On input to the PCM. It signals the PCM to raise the idle to compensate for the air-conditioning load. However, in this case the PCM only sees battery voltage on the circuit for an instant before the failing switch contacts break apart because they cannot handle the rising current flow. The PCM raises the idle speed in anticipation of the AC coming on, but lowers it again an instant later when the input signal goes away at pin 41. When the switch contacts cool off, they come back together momentarily and the cycle starts over again. The typical symptom is a regularly surging idle when the AC or defrost are turned on. This can be a tricky diagnoses, especially during the winter when you might not be thinking about air-conditioning!

Quick Tip: This circuit configuration was used by Ford for about ten years and similar versions even longer. There is a strong likelihood of a substantial voltage drop developing in the circuit as the vehicle ages. It can cause any or all of the symptoms described above. It is a good idea to check the voltage drop at the AC clutch on these vehicles when performing any kind of AC service - especially when replacing the clutch or the compressor. The voltage should never be less than 12V with the engine running and ideally should be within one volt of system voltage. This is also a good check to perform as part of a preventative maintenance check of the air-conditioning system. If the customers concern is a surging idle, monitor the A/C Cycling Switch input PID on a scan tool. If the PID momentarily changes to On intermittently, suspect that the cycling pressure switch may be no good. 2004 - 2006 Ford 6.0L Diesel E 350/450 Vans AC Compressor Failure. The AC compressor may fail. The compressor on these vehicles is a low mount scroll design. They are particularly sensitive to charge level either an undercharge or overcharge. To correct the problem, Ford has revised the refrigerant and oil capacities and also issued a calibration update for the PCM. The refrigerant charge capacities have been reduced to prevent slugging and the oil capacity of the single evaporator system increased to improve lubrication. On front AC only systems, the refrigerant charge level has been reduced to 32oz from 40oz and the oil charge level has been increased to 11 oz from 9 oz. On dual AC systems, the refrigerant charge level has been reduced to 54oz from 60oz. The oil charge level remains the same at 13 oz.


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Note: When scroll compressors suffer a catastrophic failure, they create a lot of debris. It is usually necessary to replace the condenser in conjunction with the orifice tube and the accumulator. All other components not being replaced should be thoroughly flushed including the evaporator. 2007 and Later GM Vehicles In-the-Line Filter Starting in 2007 GM began phasing in an in-the-line liquid line filter on various vehicles both cars and trucks. At first glance the filter looks very similar to an orifice tube. However, it is just a filter and there will be a separate orifice tube or TXV valve in the system. The filter simply slips into the line much the same wasy as an orifice tube. It is usually installed at at coupling in the liquid line. The filter can be found in various locations at the condensr outlet, just before the expansion device before the fire wall and on some dual evaporator applications it is located in the liquid line just before the rear TXV valve. The key is to be aware of it. If the compressor fails the filter will almost certainly be clogged. It must be replaced.

Starting 2007 - GM In-the-Line Filter Located in Liquid Line


25

Rotary Vane Compressor Issue

Saturn and Other Vehicles that Use a Rotary Vane Compressor

The customer concern is usually poor AC performance. High side pressure will be lower than normal and low side pressure will be higher. The problem often occurs after the air-conditioning system has not been used for some time. It can also occur immediately after a new or remanufactured compressor is installed. Normal diagnostics will indicate that the compressor cannot build pressure. Refer to the picture on the right of a rotary vane compressor with one end removed. When you turn a conventional piston design compressor by hand, even slowly, you can feel the suction and pressure forces at the suction and discharge ports. However, for a rotary vane compressor to start pumping, the vanes must be thrust out against the rotor sidewalls by centrifugal force. The rotor must be turning rapidly before the compressor starts to pump. When the compressor is unused for a while, the vanes may seize in their slots and not slide out against the rotor sidewalls. The problem can also occur in a perfectly good new or remanufactured compressor if it has been in storage for a while. Before condemning the compressor, try the following procedure to free the vanes:

Charge the system with half the specified amount of refrigerant. Raise the engine speed to 2500 RPM. Cycle the compressor on and off every few seconds while monitoring system pressures. If the

rotor vanes are stuck, this procedure will usually dislodge them and the compressor will start pumping again.

When the compressor starts to build pressure, add the remaining refrigerant to bring the system up to full charge. Perform a maximum heat load temperature test to confirm that the system is performing efficiently.

Note: Variable displacement compressors such as GM V5 and V7 units can suffer from a similar problem. The wobble plate can stick at a shallow angle - usually after a period of disuse. The problem can usually be corrected with the technique outlined above for rotary vane compressors. Both rotary vane and wobble plate design variable displacement compressors are especially sensitive to oil viscosity.

The Rotor Vanes Can Stick In the Slots


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Orifice Tube/TXV Dual Evaporator System Issues Here are several issues that affect General Motors Dual evaporator systems that use an orifice tube in the front and a TXV in the rear (OT/TXV). These issues can also arise on other manufacturers platforms that use a similar system.

1. These OT/TXV dual evaporator systems use an accumulator instead of a receiver/drier. This means there is no filter in the liquid line between the condenser and the rear TXV valve. (Note: Starting about 2007 GM began putting a small in-the-line filter in the liquid line of some vehicles). After a catastrophic compressor failure, it can be difficult to flush all the debris from the long lines that snake the length of the vehicle. Even with a good flushing process, some debris can remain in the lines especially in the liquid line. For this reason, it is highly

recommended that an inline filter be installed in the liquid line just before the rear TXV. The filter should be installed in addition to flushing it is not a substitute for it. Refer to the 2001 Chevy Tahoe case study on page 59 for more information on this issue.

2. Refer to the dual evaporator system schematic above. Note that the rear evaporator suction line returns directly to the compressor it is not routed through the accumulator. If liquid refrigerant or oil passes through the rear evaporator, they will return directly to the compressor and possibly slug it severe damage can result. These systems are more prone to slugging in moderate climates during low heat load conditions.

3. Another issue on some systems of this design is that the rear TXV thermal bulb can separate from the evaporator outlet line. The TXV interprets this as increased heat load and responds by metering more refrigerant into the evaporator. The excess liquid refrigerant can slug the compressor causing severe damage.

Orifice Tube

Condenser

Front Evaporator

Rear Evaporator

Accumulator

TXV

Note that Rear Evaporator Suction Line Returns Directly to Compressor Exact Charge Is Critical to Avoid Slugging

Protect TXV after Compressor Failure - Install Inline Filter

Here

TXV Thermal Bulb Detached from Suction Line Can Cause Compressor Slugging


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Various GM Trucks and Cadillac CTS 2002 2004

Compressor Noise/Failure

Affected Models: 2003-2004 Cadillac CTS 2002-2004 Cadillac Escalade and Escalade EXT 2003-2004 Cadillac Escalade ESV 2002-2004 Chevrolet Avalanche, Express, Silverado, Suburban, and Tahoe 2002-2004 GMC Denali, Denali XL, Savana, Sierra, Yukon, Yukon XL 2002-2004 Commercial Upfitter Chassis Vehicles

The symptoms vary depending on how far the failure has progressed:

The compressor may have failed outright and is inoperative. The serpentine belt and tensioner may be slapping or vibrating excessively. Pressure gauges (especially the high side gauge) may be vibrating/bouncing excessively. The compressor may be making a rattling noise, especially on acceleration.

The original compressors on these vehicles are prone to liquid slugging. Broken reed valves in the compressor usually cause the belt vibration and pressure pulsations described above. For a lasting repair, the compressor, condenser, orifice tube, accumulator and rear TXV may need to be replaced. Any sections of the refrigerant path not being replaced, including both evaporators on a dual system, should be thoroughly flushed. On a dual evaporator system, the installation of an inline filter before the rear TXV is strongly recommended. There is no receiver/drier or other filter in the system to protect the rear TXV. If a filter is not installed, the rear TXV may become restricted shortly after the repair.

2002 - 2004 Honda CR-V - Compressor Failure

These vehicles use a low mounted scroll design compressor that is prone to failure. Scroll type compressors are particularly sensitive to both liquid slugging and lack of lubrication.

Honda TSB 09-076 indicates that if evidence of debris is found in the suction line at the inlet to the compressor, then every component in the refrigerant path should be replaced compressor, condenser, drier, evaporator, all lines and hoses and the TXV.

This solution may not always be practical for many consumers. However, for a successful lasting repair, certain parts must be changed and procedures followed carefully. Note: When scroll compressors fail, they produce a lot of debris, which will be distributed throughout the AC system. At a minimum, the compressor and the condenser/receiver drier must be changed. Inspect the TXV inlet for debris and or contaminated oil. If evidence of either is found the TXV valve


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should be replaced. All other components not being replaced should be thoroughly flushed including the evaporator. Refer to the section on flushing for special tips and tools on effective flushing.

Note About Honda Condensers

These systems are very finely balanced. This system only uses 18oz of refrigerant. For the system to cool properly, every component must operate at maximum efficiency. It is not enough for the replacement condenser to look similar to the unit being removed. It must also have the same heat exchange efficiency. Compare the overall size, tube count and the fin density of the replacement condenser with the old unit they should be a close match.

2006 - 2008 Honda CR-V and Civics AC Performance Issue

Affected Models 2006 2008 Civic with automatic transmission and all 2007 - 2008 CR-Vs

The customer concern is usually a momentary drop off in AC performance under hard acceleration from below 20 mph. The problem is that the PCM is disengaging the compressor too soon on acceleration. Honda has issued a flash update to address this concern in TSB # 07-062. However, the TSB points out that compressor disengagement is normal under hard acceleration and that the symptom may not be completely eliminated by the calibration update.

Dodge Trucks - Late 1990s Early 2000s

The Customer Concern Occasionally, the AC starts blowing warm air. The problem can be very intermittent it may only occur on longer trips or during stop/go traffic. This can make it particularly difficult to diagnose. There are no diagnostic trouble codes set. The compressor clutch coil may be going open circuit intermittently. The clutch coils on some of these compressors have a higher than normal failure rate. The coil potting material cracks and exposes the coil winding leading to failure. One way to confirm the diagnosis is to monitor the voltage across the clutch with a DMM or oscilloscope and wait for the problem to occur. If the compressor stops turning but full system voltage is still available then it is probably a failing clutch coil. Compare the resistance of the clutch coil before and after the problem occurs. Also, check the air gap. An excessive gap can also cause intermittent clutch engagement.

Excess Heat has Cracked the Potting and Exposed the Clutch Coil Winding Causing Premature Failure of the Coil


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SERVICE PROCEDURES

Essential Steps for Successful Compressor Replacement

1. Replace the Accumulator or Receiver/Drier To maintain the compressor warranty, the drier must be

replaced during installation of replacement parts.

2. Replace The Orifice Tube/Liquid Line The orifice tube is the main filter in a CCOT system. If

it is not replaced, the replacement compressor will not be lubricated properly and will fail. Some orifice tube systems have the tube crimped into the liquid line. The liquid line must be replaced or an orifice tube repair kit installed to prevent compressor failure and poor system performance.

3. Inspect/Replace the Thermostatic Expansion Valve (if equipped) TXV inlets must be checked for debris or metal particles. Any

restrictions will lead to poor performance or compressor failure.

4. Flush the System With Approved Flush When the system is repaired, every inch of the refrigerant path

should be either new or flushed. Oil acts like fly paper. It will trap and hold metal debris - particularly in the evaporator. Removal of all dirty oil and debris is essential to avoid repeat compressor failure. Newer condenser designs are difficult, if not impossible to thoroughly clean, and in many cases must be replaced.

5. Add the Correct Type and Amount of Oil Oil is the lifeblood of an A/C system. Running the compressor without adequate

lubrication for even a short while will cause catastrophic damage. Unless instructed otherwise by the compressor instruction sheet, add half the oil charge to the compressor. On orifice tube systems, add the other half of the oil charge to the accumulator. On TXV systems add the other half to the evaporator. Check that you are using the correct:

Oil type: PAG, Ester or Mineral Amount Viscosity

6. Check Compressor Clutch Air Gap Before Installation The air gap is preset at the factory; however, it is a good

practice to double check it before mounting the unit. Incorrect air gap will cause poor performance or noisy operation. Air gap specs are on the instruction sheet. Check the gap at three points around the clutch.

Replace Receiver Drier, Accumulator &

Orifice Tube

Thermal Expansion

Valve (TXV)


30

7. Proper Evacuation Time The A/C system must be free of moisture and air to work properly. Single evaporator

systems should be evacuated for at least 45 minutes and dual evaporator systems for at least 90 minutes. Longer evacuations produce colder duct temperatures. A warm engine or sun-load on the vehicle will evacuation.

8. Correct Refrigerant Type and Amount Either R-12 or R-l34a should be the only refrigerants used to maintain system integrity

and warranty. The correct amount of charge is critical for proper performance. Too little and there will not be enough liquid refrigerant to carry the oil around the system; too much will slug the compressor causing irreparable damage.

9. Before First Start-up, Hand-turn The Compressor Shaft at least 15 Times with the Hose Assembly Installed

Oil and liquid refrigerant cannot be compressed. Hand turning the compressor shaft will clear oil and refrigerant from the compression area and reed valves.

10. Burnish The Clutch Assembly This process will increase the grip

between the clutch hub and the clutch pulley and enhance system performance. With the engine @ 2000 rpm, cycle the compressor clutch off and on twenty times using the A/C control switch on the dash

11. Clutch Electrical Circuit Tests Perform a voltage-drop test at the compressor clutch with the clutch engaged. Available

voltage should be within 1.5V of system voltage but never less than 12V. It is always a good practice to perform a vehicle charging system test including a battery load test as part of this procedure.

12. Proper Air Flow Through The Condenser And Radiator

Inadequate airflow through the condenser and radiator will cause excessive discharge pressures, poor performance, and compressor or clutch failure. Always clean the condenser

Check Fan Clutch Operation Bearing Play, Seal Leaks

Turn Compressor at Least 15 Times by Hand Before Start-up Use

Compressor Turning Tool


31

and radiator, check the cooling fan or fan clutch, check for air dams and radiator seals. Check between the radiator and condenser for debris. Check the coolant level in the radiator, as well as the radiator cap for pressure range and sealing.

13. Check for Leaks Use an electronic leak detector or fluorescent dye to check for leaks. A leak will cause

system failure. A job that was performed perfectly in every other way can still come back with a failed compressor if a leak goes undetected. When the refrigerant level falls too low, there will not be enough liquid refrigerant to carry the oil around in the system and maintain compressor lubrication.

14. Verify the Repair Finally, when all repairs are completed, confirm the overall

integrity and efficiency of the system by performing a Maximum Heat Load Temperature Test as described on page 63. This will help you confirm that there are no underlying weakness in the system that have not been detected before you return the vehicle to the customer.

DMM with Contact Temperature Probe


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Lubrication

Oil is the lifeblood of the AC system. Without proper lubrication, the compressor will fail quickly. R134a and PAG oil do not mix well. Maintaining lubrication in an R134a system is more difficult than it was in old R12 systems. R12 and mineral oil mixed and bonded much more easily. Even in a gaseous state, R12 still carried some oil back to the compressor.

In an R134a system, the oil is carried around the system by the liquid refrigerant. Refrigerant enters the evaporator as a liquid and evaporates as it passes through the evaporator. As the refrigerant evaporates, the oil tends to drop out. If the refrigerant charge level drops too low, there is not be enough liquid refrigerant remaining to carry the oil up and out of the evaporator and back to the compressor. The oil drops out and pools in the bottom of the evaporator. The compressor starves for oil and fails rapidly. For this reason exact system charge level is critical for proper lubrication. Cycling Clutch Orifice Tube (CCOT) Systems are particularly sensitive to undercharging.

Adding Oil

Add the specified capacity, type and viscosity of oil. Confirm this information from several sources if possible.

When performing any major service work, all of the oil should be removed from the system. Remove the compressor and accumulator / receiver drier and drain all the oil. Remove the oil from the evaporator and condenser by flushing with the proper solvent, tool and technique (read the section on flushing page 43).

Note: Multi-pass condensers should only be flushed to remove oil. If the compressor has suffered catastrophic failure these condensers cannot be flushed. They should be replaced (refer to the section on flushing).

Add half of the oil charge to the compressor and half to the accumulator or other components. Most remanufactured compressors do not contain a full oil charge. The complete amount of

specified oil must be added to the compressor through the suction port or oil plug before installing it on the vehicle.

Rotate the compressor shaft by hand at least fifteen times after all the hoses are attached but before the engine is started. This moves the oil out of the compressor to avoid liquid slugging on start up.

The old method of Oil Balancing to determine the proper amount of oil is extremely inaccurate. There are way too many variables and unknown factors. The system should be flushed and a complete system charge of oil installed.

About Oils

There are many different types of refrigerant oils in the Market, today. Mineral based to synthetic blends are available with various viscosity ranges. Mineral, parafinic, Ester, and PAG oils have been designed with certain characteristics that each compressor manufacturer has determined, through testing, to provide the best lubrication. The table following lists the type and viscosity of each oil recommended by each compressor manufacturer.


33

Compressor Manufacturer And Type Oil Type and Grade for R134a Systems and Those Retrofitted From R12

Special Notes: Virtually all R12 systems used Mineral/500 oil. Ford used a parifinic oil in the FS6 with R12. GM used a special Retrofit oil when retrofitting a V5 compressor from R12 to R134a and when not replacing the V5 compressor. Behr / Bosch Rotary Type (Make sure Comp will handle 134a)

PAG 46

Behr / Bosch Piston Type (Make sure Comp will handle 134a)

PAG 46

Calsonic V5 PAG 150 Calsonic V6 PAG 46 Chrysler RV2 PAG 46 Chrysler C171, A590, 6C17 PAG 46 Diesel Kiki / Zexel DKS, DKV, DCW PAG46 Ford FS6, FX15, FS10, FS20, 10P, 10PA, HS15, HS17, HS18, E6DH, Scroll

PAG 46

General Motors Harrison A6, R4, DA6, HR6, HT, V5, V7, HU,

PAG 150

General Motors CVC, Nippondenso and Nipp. Replacements

PAG 46

Hatachi PAG 46 Keihin (NOTE: Some Keihin compressors are not recommended to be retrofitted to R134a)

PAG 46

Matsushita FX80, FX105 PAG 100 Matsushita NL Series PAG 100 Nihon Be sure the compressor will handle R134a

PAG 46

Nippondenso 6P, 10p, 10PA, 10PO8E, SP127, SP134, 6E171 10S17, 10S20, 6C17, 6CA176, VS16N

PAG 46

Nippondenso TV PAG 100 Panasonic PAG 46 Sanden SD500 Series, SD700 Series PAG 100 Sanden SDV710, SDB Series, TV, TRS PAG 46 Seiko-Seiki PAG 100 York / Tecumseh PAG 46

All Brands of High Voltage Compressors HV Ester


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Refrigerant Recovery, Recycling and Recharging

Important Note about System Charge Level: We cannot overemphasize the importance of system charge level. Refrigerant charge capacities have been reduced dramatically over the years. Modern systems are designed to provide the same level of cooling with ever-smaller refrigerant amounts. The consequences of even an ounce or two over or undercharged can be catastrophic. It is vital to get the refrigerant charge level exactly right to avoid an expensive comeback.

Undercharged

R134a does not dissolve in PAG or POE oil. In an R134a system, the oil is carried around the system by the liquid refrigerant. Refrigerant enters the evaporator as a liquid and evaporates as it passes through the evaporator. As the refrigerant evaporates, the oil tends to separate out. If the refrigerant charge level drops too low, all the liquid refrigerant evaporates near the bottom of the evaporator. Now there is not enough liquid refrigerant to carry the oil up and out of the evaporator and back to the compressor. The oil drops out of circulation and pools in the bottom of the evaporator. The compressor starves for oil and fails rapidly. All systems will fail from lack of lubrication but Cycling Clutch Orifice Tube (CCOT) Systems are particularly sensitive to undercharging.

Overcharged

On the other hand, an overcharged system can have equally serious consequences. Liquid refrigerant may exit the evaporator and slug the compressor. Since a liquid cannot be compressed, serious damage to the compressor can result. It is not unusual to see a compressor case cracked open due to liquid slugging. TXV systems are particularly sensitive to overcharging since there is no accumulator to allow the refrigerant to evaporate before reaching the compressor.

Note: Several manufacturers have TSBs advising of revised refrigerant and oil capacities for some of their vehicles in an attempt to combat premature compressor failure.

This Scroll Compressor Failed From Lack of Lubrication The Scroll &

Rotor Are Completely Dry

Cracked Case from Liquid Slugging


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Recovery

Refrigerant recovery is important for several reasons:

1. It Is Required by Law

R134a and R12 are considered greenhouse gasses that contribute to global warming. It is illegal to vent them to the atmosphere. R12 is also an ozone depleter. These refrigerants (and others) must be recovered and appropriately processed using approved recovery/recycling equipment.

2. System Charge Level

If you are performing a normal maintenance AC service to recover, evacuate and recharge the system (without opening it up), then you need to be certain that:

All the refrigerant has been completely removed from the system before recharging it.

The amount you charge back is exactly the specified amount the system calls for.

Average system capacity has been reduced dramatically over the past 10 to 15 years. Today, system capacities of 12 to 16 ounces (oz.) are common. A few systems are even less than that. If a recovery machine failed to recover 2 oz. from a 12 oz. system and the shop tried to short circuit the service process by going straight from recovery to recharge (without evacuation) a serious overcharge could occur. When the system is charged with the specified 12 oz. it would be about 16% overcharged. Compressor slugging with catastrophic damage could occur. Note: This scenario would only happen in the event that the evacuation part of the service was bypassed in other words if you went straight from recovery to recharging without evacuating the system. Modern recovery/recycling /recharging equipment will not allow transition from recovery to recharging when in automatic mode.

Several years ago, the Society of Automotive Engineers (SAE) recognized that existing standards for refrigerant recovery equipment were not precise enough to meet the recovery and charge accuracy requirements of newer vehicles with reduced charge capacities. Studies had shown that older equipment could leave up to 30% of the refrigerant in the system during a normal recovery operation. SAE developed a new standard, J2788, for recovery/recycling/recharging equipment to meet the more exacting recovery and recharging needs of reduced capacity systems. A recovery/recycling/recharging machine meeting the J2788 standard (J2810 for recovery only equipment) must recover at least 95% of the refrigerant charge in 30 minutes or less at 70-75F ambient.

3. Quality of Recovered Refrigerant

Recovered refrigerant must be sufficiently pure and free of contamination so that it will not affect system performance or longevity when reused. Air, particulates, old oil and other contaminants must be removed. The key to maintaining high quality recovered refrigerant is proper equipment maintenance and vigilance.


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Recovered Refrigerant - Contamination

Sealer Contamination

Before connecting any equipment to a vehicle that you are unfamiliar with, use a sealer identifier to check for the presence of sealer. Undetected sealer can ruin your refrigerant identifier, recovery/recycling/recharging equipment, recovered refrigerant and contaminate the next vehicles you service. Most sealers depend on the presence of either air or moisture to work neither of which you want in an AC system. Eventually sealers coagulate throughout the system. Repairing a sealer-contaminated system will usually require replacing every component in the refrigerant path. Sealer cannot be flushed.

Air Contamination

Air is a non-condensable gas at the temperatures and pressures found in an automotive AC system. It remains in gaseous form throughout the system and takes up valuable heat exchange real estate in both the condenser and evaporator. This reduces system performance and puts additional strain on the compressor by raising system pressures. Compressor noise is often caused by air in the system. Air also supports corrosion and chemical deterioration in the system over time. This can lead to leaks and other component failures. During both recovery and evacuation, the AC system and the recovery/evacuation equipment are under vacuum. Inevitably, air will find its way into recovered refrigerant unless preventative measures are taken. Keeping air out of recovered refrigerant is like trying to keep sand out of a beach house!

Note: Most recovery/recycling/recharging machines have an automatic air-purge function. However, this feature has limitations. To check for air content these machines compare the actual pressure in the tank of recovered refrigerant with what the pressure would be in a tank of virgin refrigerant at that temperature. If air is present, the pressure in the recovered refrigerant will be higher. The auto air-purge function bleeds off

Sealer Detection Tool

Use an Air Contamination Gauge Set Attached to the Recovery Tank Vapor Port to Confirm that Recovered

Refrigerant is Free of Air. At a Stabilized Temperature, the Two Gauges Should Indicate the Same Pressure. The Top Gauge Reads Actual Tank

Pressure, the Bottom Gauge Indicates what the Pressure Would be in a Tank of Virgin Refrigerant. If

the Pressure on the Top Gauge is Higher that the Bottom Gauge then the Refrigerant Contains Air. Open the Vapor Valve Periodically Until the Two

Gauges Read the Same Pressure. It Can Take Up to 48 Hours to Completely Vent All the Air.


37

pressure in the recovery tank until the pressure in the tank is close to what it would be in a tank of pure R134a.

However, the EPA is concerned that refrigerant should not be vented to the atmosphere. They have set standards for acceptable air contamination in reclaimed refrigerant. The EPA considers 2% air contamination acceptable. Compare the pressure/temperature relationship chart on page 93 for virgin R134/R12 with the acceptable air contamination pressure/temperature chart for Reclaimed Refrigerant Contamination on page 94. Note that at a given temperature, the acceptable pressure in a tank of reclaimed R134a (or R12) is several PSI higher than it would be in a tank of pure refrigerant at the same temperature. Therefore, to avoid any possibility of venting refrigerant to the atmosphere, recovery machines typically only vent down to the higher pressure on the Reclaimed Refrigerant Contamination chart. In effect, this means that there could be up to 2% air in your recovered refrigerant.

The other concern with auto air-purge is time. It can take up to 48 hours for the trapped air in recovered refrigerant to outgas completely. As the auto air-purge function vents the recovery tank pressure down to the acceptable level, additional air will start to outgas from the refrigerant and pressure will start to build up again. It can take up to 48 hours for all the air to outgas completely from a tank of recovered refrigerant as the air-purge function goes through successive venting cycles. In a busy shop environment, as equipment is moved from one vehicle to the next, there simply is not enough time for the auto-air-purge function to vent all the air.

One solution to this issue is to use two recovery tanks. Use one tank for recovery only until it is full. Leave the machine on to allow the auto-purge feature time to vent the air. When the tank is full replace it with an empty one. Now use the stabilized tank of recovered refrigerant with a separate charging cylinder or scales for charging.

Rogue Refrigerant

Use a refrigerant identifier to confirm that the vehicle you are about to recover from is not contaminated with a rogue refrigerant. Use of refrigerants other than R12 or R134a will void your compressor warranty. A wide variety of problems can arise with the use of other refrigerants.

They may be flammable. Blended refrigerants can be unstable and separate into their component parts. The different

constituents may leak at different rates over time (due to different molecular sizes) causing the refrigerant to perform unpredictably.

They may attack materials in the system. The pressure/temperature profile will be different from R134a or R12, making diagnosis

difficult.

Recovery Recycling Only Machine


38

Recovery Quick Tips

Following are some tips to help you ensure that all the refrigerant is completely recovered from the system and that your recovered refrigerant remains free of contamination:

Maintain equipment. Perform the manufactures recommended maintenance service on schedule. Pay particular attention to the quick disconnect service couplings. They are a common source of leaks that are not always obvious - they may hold pressure but not vacuum. They are complex components with quite a number of internal parts, including several seals and springs. They are high wear items as they are repeatedly connected and disconnected from the system under pressure. Replace your machines filter regularly. J2788 machines track filter life and lock the machine down when filter is used up.

Use Heat. Heat has a dramatic effect on the rate of refrigerant recovery from a system. Servicing air conditioning when the ambient temperature is low, increases the length of time it takes to recover refrigerant from the system. In addition, as recovery begins and refrigerant starts to evaporate, it absorbs heat from its surroundings due to the latent heat of evaporation effect. This slows the recovery process even further. This is why the accumulator or receiver drier feels cold to the touch during recovery. If the drier still feels cold after recovery is apparently complete, then you know that all the refrigerant has not been removed from the system. Carefully warming the drier with a heat gun will accelerate the recovery process.

For rapid recovery, set the AC system on MAX heat and recirculate with the hood lowered. This will warm all the underhood AC components and the evaporator. Note: If the vehicle uses an electronic variable displacement clutchless compressor (see page 14) do not run the engine during recovery or if the system is low on refrigerant or oil. The compressor turns all the time the engine is running and could be damaged from lack of lubrication.

Periodically use your refrigerant identifier to check for air in your refrigerant recovery tank and also in vehicles you have just recharged.

After the vehicle is repaired, use tamper resistant shrink-on or tie-wrap system guards to seal the service ports. If the vehicle returns to you for service and the system guards are missing or have been tampered with, you know the system may have been worked on since you serviced it.

Shrink-on or Strap-on System Guards Help to Deter Tampering


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System Evacuation

A thorough evacuation produces colder duct temperatures. System evacuation is necessary to remove all air and moisture from the AC system. Air is a non-condensable gas (NCG). It remains in a gaseous state throughout the AC system and takes up valuable heat exchange real estate in both the condenser and evaporator. This reduces system efficiency. It also raises system head pressure, which increases compressor stress and noise. Air also holds moisture, which creates additional problems.

Moisture creates immediate and long-term effects in the AC system. In the short term, it freezes at the expansion device, impeding refrigerant flow and reducing performance. As the moisture freezes, refrigerant flow is reduced and the system starts to blow warm. Now the moisture starts to thaw and refrigerant flow increases. The cycle starts over again. Cycling back and forth from cold to warm is a strong indication that there is moisture contamination in the system. Moisture also holds dissolved oxygen, which can support the creation of acids and corrosive chemical activity over time. Corrosion eventually causes leaks as it eats through the thin heat exchange surfaces of the evaporator and condenser. Corrosion debris can restrict the expansion device and damage the compressor.

Following a good evacuation procedure will remove the maximum amount of air and moisture from the system. However, there are no real shortcuts. Removing moisture from the system takes time. Moisture is removed by literally boiling it from the system. The only way to get water to boil at shop temperature is to reduce the pressure on it.

The two keys to rapid, effective evacuation are a deep vacuum and heat. Refer to the Boiling Point of Water at Specific Inches of Vacuum chart on page 96. Note that vacuum must reach 29.4 inches of mercury (inHg) before water will boil at 60F. If you are evacuating a system on a 60F day and the needle on the low side gauge is pointing at 29 inHg exactly, then you are not removing any moisture from the system. 29 inHg looks good, but it is not enough on a 60F day. Referring to the chart again, we can see that on an 80F day, 29 inHg would be enough to evacuate the system eventually. However, a combination of both deep vacuum and heat are the key to rapid evacuation.

The low side gauge on a standard air-conditioning gauge set is not an accurate enough tool for assessing true vacuum. Differentiating between 29 inHg and 29.4 inHg is barely the width of the needle. A micron vacuum gauge is a much more accurate tool. For example, on a micron vacuum gauge, 29.14 inHg reads as 20,000 microns while 29.89 inHg reads as 750 microns small changes in vacuum become much more obvious.

Vacuum Looks Good at 29 But on a 60F Day Not Good Enough Must to be 29.4

Use a Micron Vacuum Gauge to Measure True Evacuation Vacuum


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To use the micron gauge, tee it into one of the service hoses as close to one of the vehicles service ports as possible. An ideal vacuum for automotive air-conditioning is less than 500 microns but below 750 microns is acceptable.

The key to achieving a deep vacuum is maintaining equipment. This means changing the vacuum pump oil frequently at the manufacturers recommended intervals. This is usually based on hours used and could mean every couple of weeks during a hot humid AC season. The other weak point in evacuation equipment is usually the service hose quick-disconnect couplings. They undergo a lot of wear and tear as they are continuously connected and disconnected to each system. Inevitably, they develop leaks. Leaks are not always obvious as they may only occur under vacuum and not under pressure. The couplings should be serviced or replaced regularly.

Evacuation Time

Single evaporator systems should be evacuated for at least 45 minutes and dual evaporator system for at least 90 minutes.

Evacuation Quick Tips

Maintain evacuation equipment. Regularly validate the ability of your vacuum pump to

pull a deep vacuum with a micron vacuum gauge. Use heat warm all the air-conditioning components

on the vehicle by running the engine with the hood lowered. Also, run the heater on max recirculate with the blower on high. This will warm the evaporator. Warming all the AC components dramatically accelerates both refrigerant recovery and system evacuation. Note: If the system uses a clutchless compressor, (where the compressor shaft turns all the time) do not run the engine without refrigerant or oil in the system.

Moisture Contaminated Vacuum Pump Oil after Just a Few Hours of Service

Change Vacuum Pump Oil at Recommended Intervals


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System Charging

Exact charge level is critical refer to the note about system charge level and the consequences of under or overcharging on page 33. System undercharging causes lack of compressor lubrication and overcharging causes compressor slugging. In either case, catastrophic consequences can result. With many system capacities now less than 1lb, old charging methods and equipment can easily result in a gross under or overcharge. Just a two-ounce undercharge on a thirteen-ounce system (e.g. some Honda Fits) amounts to a 15% error enough to cause lubrication issues.

Older equipment can be off by as much as 3 to 4 ounces on charge amount. In addition, most older equipment does not compensate for the refrigerant that remains in the hoses after charging. This can be significant up to about one ounce per foot of hose.

Charging Quick Tips

Use Recovery/Recycling/Recharging equipment that meets SAE J2788 specifications (see page 12). These machines are much more accurate than previous equipment and are specially designed to take account of the reduced charge capacities of newer vehicles. They can be programmed for the specific hose length being used on the machine.

Consider using a charging cylinder or electronic scale for charging. These are very accurate methods. Another advantage of using separate equipment is that you can improve shop productivity. By using separate Recovery/Recycling/Recharging equipment, you can service three vehicles simultaneously.

Verify and calibrate electronic charging scales with a known weight every week during peak AC season.

Service hoses that have been pulled into a vacuum during evacuation can hold four to six ounces of refrigerant, depending upon hose length and manifold design. J2788 compliant equipment automatically compensates for refrigerant trapped in the hoses. However if you are using older equipment or a separate charging scales or cylinder with a manifold gauge set, then you should manually compensate for the refrigerant that remains in the hoses after normal charging. There are two ways to do this.

1. Add about one ounce per foot of service hose to the specified charge amount. If the system specification was 20 oz. and your service hoses were four feet long, then you would set your charging machine to charge 24 oz. of refrigerant to compensate for the four oz. that would remain in the hoses.

Use a Charging Cylinder For Improved Charge Accuracy


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2. An alternative method is to draw any refrigerant remaining in the hoses into the system after the initial charge is complete. Disconnect the high side service hose from the system. Leave the low side connected. Open the high and low side manifold valves and run the engine with the AC on. This will draw any refrigerant remaining in the entire service hose and gauge assembly into the low side of the system. At low side pressure (30 40 PSI) all the refrigerant in the hoses swill be in a gaseous state. There will be virtually no refrigerant remaining in the hoses.

Let the system stabilize for several minutes before engaging the compressor clutch if liquid refrigerant has been installed in the high side. This will eliminate the possibility of slugging the compressor and breaking a piston or reed valve.

Charging by individual cans will usually lead to an undercharged condition due to the refrigerant loss that occurs when each can is change. There will always be residual refrigerant left in each can. Its only a guess, as to how much refrigerant was in the can to begin with. The other question is, how do you determine the contents of a partial used can? Another issue to contend with is the introduction of air into the system. Air can enter through the service hose as the cans are changed.


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Flushing

Note: When a system has suffered a catastrophic compressor failure, it is essential that when the repair is complete, every inch of the refrigerant path is either new or flushed this includes the evaporator. Flushing Why Is It Necessary?

To remove the failed compressors debris from any components that are not being replaced.

To remove dirty oil from the system especially from the evaporator.

A Successful Flush Requires: 1. A high quality flush solvent. A good

solvent should have the following properties: Be effective at removing oil

and debris. It must evaporate rapidly.

Any residue remaining in the system can affect system performance and cause chemical deterioration in the system over time.

Be chemically stable. It must not react with or attack materials in the system.

Be safe. Have low flammability and not be a health hazard.

Products such as brake cleaner, de-greasers, carburetor cleaners, denatured alcohol, etc should not be used as flushing agents.

2. An effective flushing tool or machine. A good flush tool should propel the flush solvent through the component b

air conditioning diagnosis service and repair v2

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