! warning tem is not correctly wired. such voltage …...turn power off before any troubleshooting...

INTEGRATED FURNACECONTROL MODULE

TROUBLESHOOTINGGUIDE

50A55 INTEGRATED FURNACE CONTROL MODULEQualifiedServiceman’sTroubleshootingGuideTROUBLESHOOTING PROCEDUREIfthelightonthemoduleisoncontinuously,thefaultislikelytobeinternaltothemodule.Tomakesure,interruptlineor24voltthermostatpowerforafewsecondsandthenrestore.Ifinternalfaultisindicatedagain,andflamesensorisnotshortedtoground,replacecontrol.Aflashinglightindicatestheproblemismostlikelyintheexternal components or wiring. Proceed as follows:

WARNING!Failure to read and follow all instructions carefully before in-stalling or operating this control, could cause personal injury and/or property damage.

WARNING!Turn power off before any troubleshooting or servicing begins.Line voltage (120 VAC) could be present on the surface of the ignitor, if the sys-tem is not correctly wired. Such voltage can cause serious injury or death.

Thefollowingstepsmustbeperformedfirstbeforeanytroubleshootingbegins.1)Disconnectelectricpowertosystematmainfuseorcircuitbreaker.2)Visuallyinspectequipmentforapparentdamage.Checkwiringforloose connections.3)Checkforpropergroundingandreversedpolarity. A. CheckcontinuityforCterminalonmoduletoelectricalservicegroundand connectionatthefurnacejunctionbox.Ifgroundconnectionisopen,check module ground connection and the electrical service ground connection. Repair and retest. B. Re-connect electric power to system. C. Checkforvoltagebetweenthelineneutralterminalandfurnaceground.If voltage exists, the main power supply lines are improperly connected to the furnace (REVERSED POLARITY). Again disconnect electric power to system; then reverse incoming supply leads to furnace. Repeat step. D. Rechecksystemforproperoperation.

If neither apparent damage, loose connection nor reversed polarity is the problem, proceed to troubleshooting chart or fault index chart that is suggested by the actualcondition.

NOTE: This troubleshooting guide is not for 50A55-4XX modules found on Trane equipmentor50A55-1XXmodulesfoundonLennoxequipment.

FAULT INDEX CHARTNo manual fan ............................................ 1A - 1KPower supply and voltage .......................... 1C - 1GNo fan at cooling speed .............................. 2A - 2LNo induced draft motor ............................... 3A - 3HLEDflashing2Xwithoutinducer................. 3ELEDflashing3Xwithinducer...................... 3I - 3OIgnitor does not glow .................................. 4A - 4DBurner does not stay lit ............................... 4E - 4NGas supply problem.................................... 4F - 4KNo outlet pressure ...................................... 4H - 4JGas valve does not energize ...................... 4L - 4NFlame sensor fault ...................................... 5A - 5PBurner ground............................................. 5KPolaritycheck ............................................. 5L - 5MIgnitor stays on after burner ignition ........... 5B - 5C

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Placethermostat

fan switch inthe ON

position.

Return fanswitch to

AUTO position.

Indoor BlowerCheck

Does indoorblower run atHEAT speed?

YES

YES

NO

NO

YES

NO

YES

NO

YES

NO

Indoor blowerfault. Repair orreplace. Check

operation.

Is 24Vpresent at

controlterminalsG & C?

Is 120Vpresent at

control terminalsCOOL & CIRNEUTRAL?

Is 24Vpresent at

controlterminalsR & C?

Does LEDflash 1 time

when disconnectis turned

ON?

Is 120Vpresent across

primary of controltransformer?

Is 24Vpresent acrosssecondary oftransformer?

Is 24Vpresent

across 12-pinconnector pins TH

& TR on thecontrol?

Is 120Vpresent at

control terminalsXFMR & XFMR

NEUTRAL?


control terminalsLINE & LINENEUTRAL?

Repair wiringfrom control to

thermostat. Checkoperation.

Repair wiringand/or plug

connection. Checkoperation.

Replacetransformer. Check

operation.

Repair wiring totransformer. Check

operation.

Correct 120Vpower supply. Check

operation.

Replace control.Check operation.


1A 1B

1E1D1C 1F

1I1H1G 1J 1K

YES

NO

YES

NO

YES

NO

YES

NO

YES

NO

CHART 1

WARNING!If diagnostic indicator (LED)

shows continuous flashing, turn off gas supply at source before disconnecting electrical power!



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Place thermostatsystem switch in

cooling mode and fanswitch in AUTOposition. Lower

temperature selectionlever to call for a

cooling cycle. R & Ycontacts close.

Return thermostatto desired

setting.

With doorswitch closed,jumper control

terminalsR & Y.

CoolingCycleCheck

Does indoorblower energize

at coolingfan speed?

YES

YES

NO

NO

YES

NO

YES

NO

Repair lowvoltage wiring to

thermostat. Checkoperation.

Doesindoor blowerenergize atcooling fan

speed?

Isthermostat terminal

Y connected to furnaceterminal Y?

Doesindoor blowerenergize atheating fan

speed?

Is 120V presentat primary oftransformer?

Is 24Vpresent at

control terminalsG & C?


control terminalsY & C?


Replacetransformer.

Check operation.

Repair wiringbetween control and

transformerprimary. Check

operation.

Correct 120Vpower supply tocontrol. Check

operation.

Repair lowvoltage wiring to

thermostat.Check operation.

Correct wiringfrom thermostat

terminal Y to Y onfurnace. Check

operation.

YESIndoor blowerfault. Repair orreplace motor.

Check operation.

NO

Is 120Vpresent at

control terminalsCOOL & CIRNEUTRAL?

2A 2B

2E2D2C 2F

2H

2K2J

2G

YES

NO

YESYES

YES

NO

NO

Is 120Vpresent at

control terminalsLINE & LINENEUTRAL?

2L

YES

Repair lowvoltage wiring

from transformer tocontrol. Check

operation.

NOIs 24V

present atcontrol terminals

R & C?

2I

NO

CHART 2



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Inducer Draft Motorand

Pressure SwitchCheck

Is induceddraft motorenergized?

YES

YESNO

Is diagnosticLED flashing 3

times?

Call for heat.Thermostat

contactsR & W close.

Jumperpressureswitch.

Disconnectelectric power

at fuse orcircuit breaker.

Is pressureswitch welded

closed?

Correct blockedor incorrectlyinstalled vent.

Check operation.

Repair leaks ininducer assembly or

replace induceddraft motor. Check

operation.

Check inducerwiring. If OK,

repair or replaceinducer motor.

Check operation.

Replace pressureswitch. Energizesystem. Check

operation.

NO

YES

NO

NO

3A 3F

Is diagnosticLED flashing 2

times?

3B

3C

3D

3G

3H

3E

3I

3J

3L

YES

NO

Ispressure

greater thanpressure switch

specs?

YES

Replace pressureswitch. Check

operation.

NO

Ispressure

greater thanpressure switch

specs?

YES

YES

NODoes ignitorglow?

Test forcontinuity acrosspressure switch.

Place inclinemanometer in

series withpressure switch

tubing.

Remove ventconnector

from furnaceflue collar.

3K

CHART 3






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Main BurnerIgnition Check.

Inducer ON.

Does ignitorwarm up and

glow?

YES YES

NONO

Does burnerignite?

Turn power OFF to furnace.Unplug ignitor from wire

harness. Connect voltmeteracross ignitor wiringharness leads fromcontrol. Energize

system.

Turn manual knob toOFF position. Connectmanometer to outlet

pressure tap. Turn knobto ON position.

Energize system.

Is 120Vpresent at

control terminalsIGN & IGNNEUTRAL?

Replace controlmodule. Check

operation.

Replace gasvalve. Energizesystem. Check

operation.

NO

YES

NO

Repair orreplace broken

leads to gas valve.Check operation.

4A 4E

4B

YES

Is gasvalve manualknob in ONposition?

4F

4C

4G

4H

4K

4N

4I

4L

4M

YES

YES

Is 24Vdetected

across gasvalve leads after

ignitor warm-up time?

Is 24Vpresent

across controlMV terminals after

ignitor warm-up time?


NO

YES

NO

Purge system ofair. Energize

system. Checkoperation.

Adjust manifoldto required

pressure setting.Check operation.

Restore gassupply at source.Check operation.

Replace ignitor.Check operation.

Replace broken ordefective wiring.Check operation.

NO NO

YES

Is outletpressure

detected afterignitor warm-

up time?

YES

Is gas atsource?

Is 120Vpresent at

ignitor leads?

4D

4JIs manifoldpressure

adjusted torequiredsetting?

YES

NO

Turn manual knobto ON position.

Check operation.

NO

Refer to servicefacts or installer’sguide for proper

pressure settings.

Connect voltmeterto gas valve

leads. Energizesystem.

CHART 4





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FlameSensorCheck

Does mainburner remain

lit?

YES NO

YESNO

Is blowerat heat speed

within 1 minuteof burner ignition?

Does ignitor remainenergized withflame present?

De-energize system.Disconnect 12-pin

connector. Connectohmmeter from flame

sensor pin FP toburner GROUND.

Replace sensor.Energize system.Check operation.

NO


YES

5A 5C5B

5E

5G

Disconnect flamesensor from wire.

Measure continuity fromwire end to FP pin

on 12-pin connector.

5IDisconnect AC power tosystem at main fuse orcircuit breaker. Connectvoltmeter from control

terminal LINE NEUTRALto BURNER GROUND.

Energize module.

5L

NO

NO

Is 120Vpresent at

control terminalsHEAT & CIRNEUTRAL?

5D

5K

5O

5H

YES

YES

Is resistanceless than

50 megohms?

Is 1 microampor morepresent?

Replace flamesensor lead. Check

operation.

NOYES

NO

Replace controlmodule. Check

operation.

Clean surface offlame sensor with

fine steel wool.Reinstall. Check

operation.

Reverse 120VLINE & NEUTRALwires. Energizesystem. Check

operation.

Repair orreplace wire.

Energize system.Check operation.

Connect groundwire from burner to12-pin connector

terminal GROUND.Check operation.

NOYES

YES

YES

Iscontrol

ground wireconnected to

burnerground?

5J

NO NO

Is sensorlead good?

Disconnect leadfrom flame sensor.Connect ohmmeter

from sensor toburner ground.

5NConnect a microammeter

in series with flamesensor and sensor

lead. Energize system.Measure current when

burner ignites.

5F

Is resistanceless than

50 megohms(50,000,000

Ohms)?

5M

Is 120Vpresent at

burner ground?

NO

5PRemovesensor.

Does sensorhave carbon ordust buildup?

YES

Repair wiringand/or replaceindoor blowermotor. Check

operation.

System isfunctioning

properly.

YES

CHART 5






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! warning tem is not correctly wired. such voltage …...turn power off before any troubleshooting...

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