mgtc electrical circuits v1mgtc electrical circuits revision log this is a working document, as such...

MGTC Electrical Circuits RichardStormsAbingdonRoughRidersDecember2018Version1.1

MGTCElectricalCircuits

TableOfContents

Introduction..............................................................................................................................1Background.........................................................................................................................................1Nomenclatures...................................................................................................................................2ABitofHistoryandConfusion......................................................................................................2References...........................................................................................................................................3

MultipleCircuitComponents...............................................................................................4RF95ControlBox..............................................................................................................................4Lighting&IgnitionSwitch..............................................................................................................5HornPush&DipperSwitch...........................................................................................................6Ammeter..............................................................................................................................................7

BasicCircuits.............................................................................................................................8BatteryChargingandPowerSupply...........................................................................................8Generator............................................................................................................................................................8RF95ControlBox............................................................................................................................................8VoltageRegulatorCircuit.............................................................................................................................9TheCut-OutCircuit......................................................................................................................................10TheChargingandAuxiliaryPowerCircuits......................................................................................11TheIgnitionWarningLightCircuit.......................................................................................................12

Ignition..............................................................................................................................................13Coil......................................................................................................................................................................13IgnitionCircuit...............................................................................................................................................13Condenser........................................................................................................................................................14

Headlights.........................................................................................................................................15SideandTailLights.......................................................................................................................16StopLight..........................................................................................................................................17Horn....................................................................................................................................................18Dash/PanelLights,ClockandInspectionSockets...............................................................19FogLightandPetrolWarningLight.........................................................................................20MapLights.........................................................................................................................................21PetrolPump.....................................................................................................................................22ScreenwiperMotor........................................................................................................................23

CircuitVariations.................................................................................................................24SingleDipHeadlamp–Variation1and4...............................................................................2430MPHWarningLight–Variations1and4.........................................................................25MapLightwith30MPHWarningLight–Variations1and4...........................................26

OptionalCircuits...................................................................................................................27DirectionalIndicatorLightsandStopLights........................................................................27TheDB10DirectionalRelayInternals.................................................................................................27TheFlasherUnit............................................................................................................................................29DirectionalIndicatorCircuits..................................................................................................................30

Appendix.................................................................................................................................31UsedWireNumberandColorsbyWireNumber.................................................................31CrossReferenceofRevisedandEarlyUsedColors.............................................................32


RevisionLogThisisaworkingdocument,assuchchangeswillbemadeasnewinformationemerges,enhancementtoimprovethereadabilityorerrorsarefound.Belowisalistoftheseupdates.December23,2018–Version1.0InitialIssueDecember27,2018–Version1.1Updates

• Addedsectioncalled“ABitofHistoryandConfusion”• AddedAmmetertolistofMultipleCircuitComponents• RevisedtheCircuitVariantsdiagrams• RevisedtheAppendixregardingcolorcodes


27December2018 Version1.1 Page 1

IntroductionBackgroundIputthispapertogetherasaprojecttoeducatemyselfontheindividualelectricalcircuitsusedontheMGTC.ThiswaspromptedbythenumberoftimesIwaschallengedtotrackdownaproblemandwasfacedwithwhatIfeltwaspoordocumentation.Imeanhaveyoueverattemptedtotraceanelectricallineusingtheschematicdiagramsinanyofthereferencemanuals?Andthenthevariations,theinstructionmanuallistsfivevariations:

1. M.G.Midget(Series“TC”)1945/8Home! Earlycolorcodeseries! SingleDipFilament–Leftside! 30MPHWarningLight

2. M.G.Midget(Series“TC”)1945/8R.H.D.andL.H.D.(Export)

! Earlycolorcodeseries! DualDipFilament

3. M.G.Midget(Series“TC”)1948R.H.D.andL.H.D.(Export)

! Revisedcolorcodeseries! DualDipFilaments

4. M.G.Midget(Series“TC”)1948/9Home

! Revisedcolorcodeseries! SingleDipFilament–LeftSide! 30MPHWarningLight

5. M.G.Midget(Series“TC”)1948/9U.S.A.(Export)

Thisisthe“EXU”model,whichcontainsanumberofmodificationsincluding:! DirectionalIndicators! MultipleStopLights! NoFogLamp! DualHornsunderthebonnet

ForthispaperIamusingthevariationnumber3forschematicsandcolorschemes,mostlybecausebothmycarsare1948’sandusethisvariation.However,whenlookingatthediagramsIseeverylittledifferencesbetweenthefirst4variations.Theonlyrealexceptionisforthe“EXU”model.TobeasinclusiveaspossibleIhaveincludeddiagramstocoverthe“exceptions”notedforvariations1and4.Variation2isthesameasVariation3exceptforcolor.Onelastpoint,Idonotprofesstobeanyformofexpertonelectronics.AlltheinformationIampresentinghereisextractedfromnumerousreferencesanddirect



observationoftheelectricalsysteminmycars.Shouldyoudetectanerror,pleaseletmeknowatTCStormer@comcast.netandIwillupdatethedocument.NomenclaturesSomenotesregardinglabelingofitem:

! Inallcases“Left”isthepassengerside,“Right”isdriver’sside.! LHisLeftHand,RHisRightHand! SWisSwitch! w/standsforWith! ThenamesGeneratorandDynamoareinterchangeable.Ihavechosentouse

Generator! LampandLightareinterchangeable.IhavechosentouseLight,exceptfor

theD-Lampname.ABitofHistoryandConfusionThelabelingofindividualwiresinalldocumentationhasbeenbywirenumberalongwithachartthattranslatesthatnumbertocolors.Intheearlycars,1945tosometimein1948theworksuseda33-colorchartasseenontheright.ThesecarsarereferredtointheBrownBookas“M.G.MIDGET(Series“TC”)1945/8Home”(Variation1above)and“M.G.MIDGET(Series“TC”)1945/8R.H.D.andL.H.D.(Export)”(Variation2above).Thenin1948achangewasmadetoexpandthecolorchartto64colorsasshownbelowandreassignthewirenumberstocolorreference.ForexampleRedintheoldchartis“1”,inthenewchartit’s“41”.



TheconfusionbeganwhenreprintsoftheBrownBookusedthe64-colorchartasreferencetotheVariation1and2layouts.DougPelton,ofFromTheFrameUp,inhisTechTip“EL960Wiringdiagramerrorsandcorrections,earlyTC”,reportedthiserror.WhencheckingtheindividualcircuitswirebywireandtheirwirenumbersbetweenVariations1and2versusVariations3and4,wefindthattherearesixnumber/colorcombinationsthatactuallylineup.Theyare: 33ColorChart 64ColorChart 1 Red 41 Red 2 Red&Yellow 42 Redw/Yellow 20 White 9 White 25 Yellow 8 Yellow 31 Purple 49 Purple 33 Black 57 BlackAllremainingcircuitwirecolorsdonotlineup.ForexampleintheearlycarsthewirebetweentheStarterandtheAmmeterislabeledas13orYellow&Blackandinthe1948andlaterit’slabeledas33orBrown.Sotheearlycarstrulyhadadifferentcolorscheme.PleaserefertotheAppendix–CrossReferenceofRevisedandEarlyUsedColorsasaguidefortranslatingtheearlycolorstotherevisedcolorsinthefollowingdiagrams.ReferencesLucas/TechnicalService/OverseasTechnicalCorrespondenceCourse

! Section3,CoilIgnition! Section4,Generators,and! Section5GeneratorOutputControl.Thisseriesalsoservedasthesourceofsomeoftheillustrations.

Thefullsetofthesemanualsisavailableonlineat

https://www.fromtheframeup.com/Lucas_Manual_CTYJ.htmlNoAuthorListed.1954,TheInstructionManualfortheMGSeries“TC”MidgetBall,Kenneth.1968,MGAutobookOneBlower,W.E.1952,TheMGWorkshopManualFrom“M”Typeto“T.F.1500”ForreferencesontheuseoftheDB10DirectionalRelayIreliedheavilyonawebsitecalled‘TheMGAwithanAttitude”-https://www.mgaguru.com/mg01.htm.Specificallyhttps://mgaguru.com/mgtech/electric/et105.htm,andhttps://mgaguru.com/mgtech/electric/et104.htm



MultipleCircuitComponentsFourofthecomponentsareusedinmultiplecircuits.Sinceeachcircuitdescriptiononlydealswiththewiringthatisusedbyjustthatcircuit,I’mincludinganoveralllookofalltheconnectionsusedbyeachofthesecomponents.RF95ControlBoxPleaserefertotheBatteryChargingandPowerSupplysectionforafulldescriptionofthepowerflowwithintheControlBox.

A1

A

A2

F

D

A4

A4 A3

E

Lighting & Ignition Switch

Ammeter

Horn

Generator Generator

Fog Light Switch Stop Light Switch

Screen Wiper Motor

Ground Horn Push & Dipper Switch Petrol Pump Screen Wiper Motor

Coil Lighting & Ignition Switch

Black

White

Green

Green Yellow w/Green

Purple

Brown w/ White

Brown w/ Blue

Yellow



Lighting&IgnitionSwitchPowerenterstheswitchatconnectionA(Input)andexitsthroughIG(Ignition),H(Headlights)andT(TailandSideLights).ConnectionL(Lighting)isnotused.WhenthekeyisturnedonaconnectionismadebetweenAandIG,whichthenconnectstoterminalA3ontheRF95ControlBox.All“IgnitionOn”circuitsarecontrolledbythisconnection.SettingtheswitchtoS(Side/Tail)willcreateaconnectionbetweenAandT.WhensettoH(Headlights)thisconnectsAtobothHandT.

D-Lamp(s) LH Side Light RH Side Light Panel Light Switch

A

IG

H T

L

RF95 Control Box

RF95 Control Box Ignition Warning Light

Horn Push & Dipper Switch

Brown w/Blue

White

Blue

Red



HornPush&DipperSwitchSincetherearenopre-assignedconnectionidentifiers,Ihavetakenthelibertytogiveeachpointofattachmentalettercode.Theseare:H(Headlight),M(Main),D(Dip),P(Push)andE(Earth).PowertotheswitchisviaconnectionHandthenbasedontheswitchsettingiteitherleavesbyofM(Honthefrontoftheswitch)orD(Donthefrontoftheswitch).WhenthebuttonispushedaconnectionismadefromEtoP.Anoteofinterest,onallthewiringdiagrams,itshowsthattheHornandtheheadlightMainconnectionsarereversed,thatis,HornonthetopandMainonthebottom.Yet,thephysicalswitchisasshownbelow.Additionally,thediagramsshowadedicatedconnectionfortheEarth.Inbothofmycars,thereisnodedicatedconnectionandtheEarthisactuallyconnectedtothemountinglug.

M D LH Headlight (Dip) RH Headlight (Dip)

LH Headlight (Main) RH Headlight (Main)

H P

E

Horn Lighting & Ignition Switch

RF95 Control Box

Blue w/White Blue w/Red

Purple w/Black Blue

Black



AmmeterNotethelabelingofBandAisconsistentinallthewiringdiagrams.

B A

Brown Brown w/White RF95 Control Box Starter

Inspection Lamp Socket Map Reading Light



BasicCircuitsBatteryChargingandPowerSupplyTheBatteryChargingCircuitisnodoubtthemostcomplexofallcircuitsintheTC.Thereareanumberofcomponentsthatgointothemakeupofthiscircuitandeachhasaparttoplay.ThethreemainplayersaretheBattery,theGeneratorandtheRF95ControlBox.InadditionitusestheAmmeter,theLighting&IgnitionSwitch,andtheIgnitionWarningLight.Thiscircuitdoesmorethanjustchargethebattery.Itisalsoresponsibleforprovidingandcontrollingthepowerforallelectroniccomponentsinthecar.Tounderstandwhythingshappeninthiscircuitit’snecessarytoexamineboththeGeneratorandtheRF95ControlBox.GeneratorThegeneratoraffixedtoourTC’sisa“shunt-wound”typedesign.Thesegeneratorsoutputdirectcurrentinwhichthefieldandarmaturewindingsareconnectedinparallel,andthearmature,connection“D”,suppliesboththeloadandthefieldcurrent.Becauseofthisit’snecessarythatyouareawareofonlytwothings:

• Thetwooutputterminals;“D”and“F”mustbeconnectedtoeachotherinordertocompleteacircuitthusproduceelectricaloutput,and

• Thatthefasterthegeneratorspins,themorepoweritwilloutput.

BothoftheseitemsarethereasonthereisaRF95ControlBox.RF95ControlBoxTheRF95ControlBox,sometimesreferredtoasa“regulator,”istheheartofmaintainingaproperchargeinthecar’sbattery.Itservesthreefunctions;

• VoltageRegulator-EnsuringthattheoutputfromtheGeneratoriskeptatasafelevel

• TheCut-Out–Providestheactualchargingcircuitforthebattery,auxiliarypowerwhenadditionalcomponents,suchasheadlights,areused,andprotectsthebatteryagainstGeneratorfailureorwhenthecarisrunningsloworidling,and

• Actsasaterminalstripforconnectingwires



Thefirsttwofunctionsarecontrolledbytheuseoftwoelectro-magnets.AsyoulookattheControlBox,theelectro-magnetontheleftistheVoltageRegulatorandtheCut-Outisontheright.Theyeachprovidethesamebasicfunction,toconnectordisconnectacircuit.It’simportanttonote,thateventhoughtheGeneratorpowersboththeseswitches,theyactindependentlyofeachother.Beforejumpingintohowitworks,it’snecessarytoreviewthebasicconstructionoftheunit.Themajorpartsare:

• TheIronFrameorYoke(1)• TheIronBobbinsorElectro-Magnet(2)• ApivotedbracketorArmature(3)• TheMountingSpringBlade(4)• TheMoveableContact(5)• TheFixedContact(6)• TheTensionSpringBlade(7),and• TheAdjustingScrew(8)

Bothoftheelectro-magnetswitchesareidenticalexceptforoneitem,theContacts(5&6).OntheVoltageRegulatorthecontactsareclosedwhentheswitchisatrest,thatis,whennopowerisrunningthroughthesystem.AndtheContactsontheCut-Outswitchareopenwhentheswitchisatrest.ThepurposeoftheTensionSpringBlade(7)andAdjustingScrew(8)istomaintainthepropermagneticpullnecessarytomovetheArmature.Thistensionissetbythemanufactureandisbasedongeneratormodel.VoltageRegulatorCircuitAsdiscussedinthesectionabouttheGeneratorweknowthattheGeneratorwillputoutmorevoltswhenspunatahigherspeed.Withoutregulatingthisoutput,itispossibletooverchargethebatteryand/orburnouttheGenerator,thustheVoltageRegulator.Controllingissimple.IfwebreaktheD/Fconnection,thenpoweroutputfromtheGeneratorwillfalloffloweringtheoutputvoltage.TheregulatingcircuitbeginswiththeGenerator.OutputissentthroughterminalDtotheControlBoxwhereitisconnectedtoterminalDandtheYoke(1).FromthereittravelsacrosstheMountingSpringBlade(4),downtheArmature(3),acrosstheContacts(5&6),thenreturnstotheGeneratorviaTerminalFtocompletethecircuit.



Tobreakthiscircuit,weneedtoopenuptheContacts(5&6).ThisisdonebytheuseoftheBobbin(2),whichisanelectricalmagnet.Ithasanironcorewithfinecopperwirewrappedaroundit.WhenpowerfromtheGeneratorisappliedtothecopperwoundBobbin(2),itturnstheironcoreintoamagnet.Themorepowerthestrongerthemagnet.AstheoutputfromtheGeneratorincreasestheelectro-magnetbecomesstrongeruntilitovercomestheTensionSpring(7)topulltheArmature(3)down.ThisactiondisconnectstheContacts(5&6),breakingtheD/Fcircuit.PowerfromtheGeneratorfallsoffassoonasthecircuitisbroken.Thereducedpowerthencausestheelectro-magnettoloosepower.ThemagneticpullisreducedandtheArmature(3)isreleasedfromthemagnetandthecontactsarejoinedagainreconnectingtheD/Fcircuit.Thenthewholecyclebeginsagain.Thisentireprocessrepeatsbetween60and100timespersecond.TheresultofallthisisasmoothregulatedpowerflowfromtheGenerator.TheCut-OutCircuitTheCut-Outcontrolstheflowofpowertothebatteryforrechargingandtheauxiliarypowerrequiredwhenadditionalelectricalcomponents(e.g.Headlights)areinuse.ItalsoperformstheimportanttaskofnotlettingthebatterydischargethroughthegeneratorfieldwindingsshouldthegeneratorfailorwhentheengineisrunningatslowRPM’s.Thechargingcircuitisliketheregulatorcircuit,exceptthatwewanttoconnectacircuitthatrunsfromtheGeneratortothebattery.Sincethecontacts(5&6)are“normally”open,itbecomesnecessarytoclosethesecontactsinordertocompletethistask.Forthiswewillstartwiththeelectro-magneticcircuit.PoweragainstartsatthegeneratorwiththeoutputfromTerminalD,thentotheRF95ControlBoxTerminalD,thentheYoke(1)andtothecopperwindingsaroundtheBobbin(2).AsoutputfromtheGeneratorincreases,sotodoesthepoweroftheelectro-magnet.AgainwhenthemagnetbecomespowerfulenoughitwillmovetheArmature(3)downcausingtheContacts(5&6)toclose.



WiththeContactsclosed,powerfromtheGeneratorwillflowviaTerminalD,totheYoke(1),acrosstheMountingSpringBlade(4),downtheArmature(3),throughtheContacts(5&6),acrosstheHeavyCoilsontheoutsideoftheBobbins(2)andoutTerminalsA1andA.TheothermajorfunctionoftheCut-OutisprotectingtheBattery.WhentheGeneratorfailstoproduceenoughpower,eitherbyslowerspeedsorfailure,thentheContacts(5&6)willopen.Ifthisdidnothappen,thenpowerfromtheBatterywouldflowbackwardsthroughthesystem.FromtheBatterytotheStarterSwitch,acrosstheAmmeter,toTerminalA,theHeavyCoils,acrosstheContacts(5&6),thentheArmature(3),downtheYoke(1)outTerminalDandtothewindingsintheGeneratorandtotheground.ThiswouldresultindrainingtheBattery.TheChargingandAuxiliaryPowerCircuitsNowthatwehavepowerfromtheGeneratorthroughtheRF95ControlBoxfeedingthesystemviaTerminalsA1andA,letsseehowthesecircuitswork.OutputfromtheGeneratorthroughTerminalAontheControlBoxissendingpowertothe“A“sideoftheAmmeter,whichisthenconnectedtotheBattery.AtthesametimetheBatteryisattemptingtosendpowerinoppositedirection.ButthismeansthatwehavepowerfromboththeBatteryandtheGeneratorbeingsentintothesamecircuit.Whenthishappens,oneofthreethingswilloccur.

• IftheoutputfromtheBatteryandtheGeneratorareboththesame,thenthetwoopposingelectricalforceswillresultinnocurrentflow,andtheAmmeterwillshowneithernegativenorpositivecharging.OutputfromtheGeneratorwill,however,flowfromTerminalA1andthentoconnectionAontheLighting&IgnitionSwitchandontovariouscomponentsbywayoftheIG,HandTconnections.

• IftheGeneratoroutputisgreaterthantheBattery,thenthecircuitwillflowfromtheGeneratortotheBatteryviatheControlBox’sTerminalAandtheAmmeterwillregisterapositivebatterycharging.TheelectricaloutputwillalsoflowthroughTerminalA1totherestofthecarviatheLighting&IgnitionSwitchconnectionAandoutviaconnectionsIG,HandT.



• IftheBatteryisgreaterthantheGeneratoroutput,thenpowerwillflowfromtheBattery,throughtheAmmetertoTerminalAthenacrosstoTerminalA1andthentoconnectionAontheLighting&IgnitionSwitchandoutviaconnectionsIG,HandT.ThiswillresultintheAmmetershowinganegativechargeandthebatterywillpowerallelectronicsinthecar.

TheIgnitionWarningLightCircuitSohaveyoueverwonderedwhytheredlightcomesonwhentheGeneratorisnotproducingoutput?Imeanittakespowertomakethelightcomeon,butnopower?Tosolvethismysteryweneedtoreviewitscircuit.StartingattheBattery,thecircuitattachestotheAmmeterterminalB,acrossthegauge,outterminalA,thenontotheRF95ControlBoxatterminalA.ThenoutterminalA1whereitattachestotheLighting&IgnitionSwitchatconnectionA.Assumingthekeyison,powerthenexitstheswitchatconnectionIGwhereitattachestoonesideoftheIgnitionWarningLight.TheothersideoftheLightisattachedtoterminalDoftheRF95ControlBox.TerminalDisthengroundedviatheControlBox,thuscompletingthecircuit.Iftheengineisnotrunningorrunningslow,andthereforlittleornopowerisbeingproducedbytheGenerator,thenelectricitywillflowthroughthecircuit,fromthebatterytotheRF95ControlBoxandthelightwillcomeonbeingpoweredbythebattery.Whenthecarstarts,andthegeneratorproducesenoughoutputwhichisequaltoormorethanthebatteryoutput,thenthetwoopposingflowswillcanceleachotherout,nopowerwillflowthroughthecircuitandthelightwillgoout.



IgnitionTheIgnitionCircuitisrathersimpleone,wirewise,onlyafewconnections.ButliketheChargingcircuitthereisanelementthatdeservesamorein-depthreview,theCoil.CoilThepurposeofthecoilistobuildupenoughpowertocreateasparkacrossthesparkpluggapinordertoignitetheair/fuelmixtureinthecylinder.Toaccomplishthistherearethreeparts:

• ThePrimaryCoil• TheSecondaryCoil,and• AMagneticFieldgeneratedbythe

PrimaryCoil.BoththePrimaryandSecondaryCoilsarewindingsaroundanironcore.WhenpowerisappliedtothePrimaryCoils(showinbold)thiscreatesastrongmagneticfieldwithintheironcore.Whenthedistributorpointsopen,thecurrentwillstopflowingandtheMagneticFieldcollapses.HoweverthecollapsewillinduceacurrentimpulseinthefinewindingsoftheSecondaryCoilthatcan,basedonthenumberofwindings,produceanoutputof20,000voltsexitingtheCoilthroughtheH.T.(HighTension)andconnectiononthetopoftheDistributor.IgnitionCircuitAswithallcircuitswebeginwiththebattery,acrosstheAmmeterandconnectstotheRF95ControlboxatterminalAthroughtheexternalcoilandontoterminalA1.ThereitisjoinedwithoutputfromtheGeneratorandexitstheControlBox.FromthereitattachestotheLightingandIgnitionSwitchatconnectionA.WhenthekeyisturnedonthecurrentleavesviatheIGconnectionandattachestoTerminalA3oftheControlBoxandontotheSW(Switch)sideoftheCoil.ThepowergoingtothePrimaryCoilwillleavetheCoilusingtheCB(ControlBreaker)connection,andthenontotheDistributorattachtotheL.T.(LowTension)terminal.InsidetheDistributor,thecircuitcontinuesacrosstheclosedpointsandfinallytoearth.



PowerbuildsintheMagneticField,andwhentheStarterSwitchispulledtheDistributorwillrotatecausingtheContactPointstoopenandclose.ThisactionwillcausetheCoiltoperforminthemannernotedabove.WhentheMagneticFieldcollapsesandconvertstohighvoltageviatheSecondaryCoilitexitstheCoilthroughtheH.T.connectionandenterstheDistributorCapviaitsH.T.connection.Fromthereitissenttothesparkplugsbywayoftherotor.CondenserThereisonemoreitemtocover,theCondenserunderthedistributorcap.ThetermCondenserisanengineeringtermthatcoversanumberofitems,oneofwhichisthecylindricalitemattachedtothepoints.Inelectronicsit’scalledacapacitor.Capacitorsareusedinelectroniccircuitstostoreandreleaseelectricityinordertoensurethattheflowofelectricityissmooth.Thisisespeciallyimportantinitemssuchassoundsystems,computersandmeasuringdeviceswhereuninterruptedsupplyiscritical.Inourcasethecapacitororcondenserisusedtoprotectthepointsbydrainingoffunwantedvoltage.WhenthepointsopenandthePrimaryCoilcircuitdisconnect,andthelargesurgeofpowerleavesviatheSecondaryCoils,anewinducedvoltageoccursinthePrimaryCoils,whichcanrisetoashighas250to300volts.ThishappensjustasthepointsopenandthisvoltageenterstheDistributorviatheL.T.connection.Withoutthecapacitor,thevoltswouldsparkacrossthepointsinanattempttoreachthegroundcausingseverdamagetothepoints.Withthecapacitor,theextravoltageisstoredinthecapacitorandthenreleasedontheothersideandtotheground.



HeadlightsPowerSource: Batteryand/orGeneratorIgnitionOnorOff: EitherSwitchSettings: Lighting&IgnitionSwitch: H HornPush&DipperSwitch: DorHPowerstartsattheBattery,acrosstheAmmeter,totheControlBoxatterminalA,acrosstheexternalcoils,thenjoinswithoutputfromtheGeneratoratterminalA1.FromthereitgoestoconnectionAontheLighting&IgnitionSwitch.WhentheLighting&IgnitionswitchissettoH(Headlights)aconnectionismadebetweenconnectionAandconnectionH,whichthenconnectstoHontheHornPushandDipperSwitch.TheDipperSwitchcanbesettoeitherD(Dip)orH(High/Main),whichconnectstothecorrectfilamentontheheadlights.Thecircuitiscompletebywayoftheheadlightbucketsgroundedtotheframe.



SideandTailLightsPowerSource: Batteryand/orGeneratorIgnitionOnorOff: EitherSwitchSettings: Lighting&IgnitionSwitch: SorHPowerstartsattheBattery,acrosstheAmmeter,totheControlBoxatterminalA,acrossthecoils,thenjoinswithoutputfromtheGeneratoratterminalA1.FromthereitgoestoconnectionAontheLighting&IgnitionSwitch.WhentheLighting&IgnitionSwitchissettoS(SideLights)orH(Headlights)aconnectionismadebetweenconnectionAandconnectionT,whichthenconnectstobothSideLightsandtheD-LampTailLightfilaments.FinalcompletionofthecircuitisviatheindividuallightbucketsandDLamp(s)beinggroundtotheframe.



StopLightPowerSource: Batteryand/orGeneratorIgnitionOnorOff: OnSwitchSettings: N/APowerstartsattheBattery,acrosstheAmmeter,totheControlBoxatterminalA,acrossthecoils,thenjoinswithoutputfromtheGeneratoratterminalA1.FromthereitgoestoconnectionAontheLighting&IgnitionSwitch.WhentheignitionkeyisturnedonthecurrentleavestheLighting&IgnitionSwitchviatheIGconnectionandattachestoTerminalA3thatisconnectedtotheA4terminalsbywayofafuse.PowercontinuestotheStopLightSwitch.WhenthebrakesareappliesitclosestheStopLightSwitchandconnectswiththeD-LampandtheStopLightfilament.TheDLampgroundcompletesthecircuit.Note:WhenusingtheDB10DirectionalRelay,theconnectionfromtheStopLightSwitchisnotsentdirectlytotheD-Lamp.InsteaditisroutedtoConnection5ontheDirectionalRelay.



HornPowerSource: Batteryand/orGeneratorIgnitionOnorOff: EitherSwitchSettings: HornPush&DipperSwitch: HornButtonPushedThiscircuitstartswiththebattery,acrosstheAmmeterandconnectstotheRF95ControlboxatterminalAandontoA1thenconnectstoA2viaafuseandflowstotheHorn.TheothersideofthecircuitbeginsattheHornPush&DipperSwitch.WhenthebuttonispusheditmakesaconnectionwiththegroundandconnectionP(forPush),thuscompletingthecircuitandtheHornhopefullysounds.



Dash/PanelLights,ClockandInspectionSocketsPowerSource: Clock: Battery Dash/PanelLights: Batteryand/orGenerator InspectionSockets: BatteryIgnitionOnorOff: EitherSwitchSettings: Clock: N/A InspectionSockets: N/A Dash/PanelLight: Lighting&IgnitionSwitch: SorH DashLightSwitch: OnTherearetwosourcesofpowerforthiscircuitdiagram.TheClockandtheInspectionLightSocketderivetheirpowerdirectlyfromtheBatteryviatheBconnectionontheAmmeter.TheDash/PanelLight,however,obtaintheirpowerfromtheA1terminalontheRF95ControlBoxviatheLighting&IgnitionSwitch.ButtheyallgettheirgroundconnectionfromtheearthsideoftheInspectionLampSockets.FortheDashLightstheLightingandIgnitionSwitchmustfirstbesettoeitherSforSideorHforHeadlight.FromthereitexitsatconnectionTandattachestoonesideoftheDashLightsSwitch,whichfeedstheDashandPanelLights.GroundingiswayofadedicatedwirethatattachestothegroundedInspectionLampSocket.



FogLightandPetrolWarningLightPowerSource: Batteryand/orGeneratorIgnitionOnorOff: OnSwitchSettings: FogLightSwitch: On PetrolLight: N/AThisseemslikeastrangecombination,butheckgrabanyconnectionthat’savailable.AsbeforepowerisfromtheBattery&GeneratormeetingattheA1terminal,fromtheretotheLightingandIgnitionSwitch.WhenthekeyisturnedonpowerflowsbacktotheControlBoxandattachesatterminalA3,thenacrossthefusetoterminalA4.ConnectionisthenmadetotheFogLightSwitch,whichmakesaconvenientconnectionforthePetrolWarningLight.WhentheFogLightSwitchisturnedon,thepowerflowtotheFogLight,whichcompletesitscircuitthroughtheFogLightbucketgroundtothecarframe.ForthePetrolWarningLight,poweristakeofftheFogLightswitchandconnectstoonesideofthePetrolWarningLight.TheothersideofthelightisconnectedtothePetrolSendingUnitmountedonthebackofthepetroltank.WhenthefueldropsthefloatarminsidemovesdownwardallowingtheSendingUnittocompleteagroundconnection,andlettingusknowit’stimetofillup.



MapLightsPowerSource: BatteryIgnitionOnorOff: EitherSwitchSettings: MapReadingLightSwitch: OnNexttotheClock,thisisnodoubtthesimplestcircuitonthecar.PowerstartsattheBattery,whichconnectstoterminalBoftheAmmeter.FromthereseparatelinesattachtoeachoftheMapReadingLight.Tocompletethecircuit,dedicatedgroundlinesarerunfromeachMapLighttothegroundedInspectionLampSocket.Therearenoexternalswitches,insteadrelyingontheinternalswitchineachoftheMapReadingLightunits.



PetrolPumpPowerSource: Batteryand/orGeneratorIgnitionOnorOff: OnSwitchSettings: N/APowerstartsattheBattery,acrosstheAmmeter,totheControlBoxatterminalA,acrossthecoils,thenjoinswithoutputfromtheGeneratoratterminalA1.FromthereitgoestoconnectionAontheLighting&IgnitionSwitch.WiththeIgnitionSwitchturnedon,powerexitsatconnectionIGandattachestoterminalA3ontheControlBox.FromthereaseparatewireconnectstotheSWsideoftheCoilandcontinuesontothetopconnectiononthePetrolPump.AnotherwireconnectedtothesideofthePetrolPumpthenreturnstotheControlBoxandconnectionatterminalEinordertoprovideagroundforthecircuit.



ScreenwiperMotorPowerSource: Batteryand/orGeneratorIgnitionOnorOff: OnSwitchSettings: ScreenwiperSwitch: OnAnothersimplecircuit,althoughthewiringdocumentationshowsthisbeingwireddirectlytotheRF95ControlBox,thesewiresarenotincludedinthewiringloom.MostpeoplefindconventplacesbehindthedashtoconnecttheScreenwipermotor.PowerflowsfromtheLightingandIgnitionSwitchviatheIGconnectiontotheA3connectionontheControlBox,acrossthefusetoA4,thenontotheScreenwiperMotor.WhentheWiperSwitchisturnon,thecircuitiscompletedviaasecondwiretotheControlBoxattachedtotheEterminalandtheearth.



CircuitVariationsSingleDipHeadlamp–Variation1and4PowerSource: Batteryand/orGeneratorIgnitionOnorOff: EitherSwitchSettings: Lighting&IgnitionSwitch: H HornPush&DipperSwitch: DorH



30MPHWarningLight–Variations1and4PowerSource: Batteryand/orGeneratorIgnitionOnorOff: OnSwitchSettings: N/A



MapLightwith30MPHWarningLight–Variations1and4PowerSource: BatteryIgnitionOnorOff: EitherSwitchSettings: MapReadingLightSwitch: On



OptionalCircuitsDirectionalIndicatorLightsandStopLightsDirectionalIndicatorLights(TurnSignals)werefirstaddedtoaTCbythefactorywiththeEXUmodel.RetrofittingtheolderTCswiththisoptionrequiressomemodificationstothecarandafairamountofnewelectricalwiring.Itis,however,averycommonpractice.Toperformthismodificationrequiresthefollowingnewitems:

• Replacingthefrontsidelightssocketswithonesthatacceptadoublefilament

• AddingasecondD-Lamp• Addingrearturnsignallamps• AddingtheDB10DirectionalRelay• AddingaFlasherUnit• AddingaDirectionalSwitch

BeforewelookattheDirectionalIndicatorcircuit,weneedtounderstandhowtheRelayandtheFlasherunitswork.TheDB10DirectionalRelayInternalsTheDirectionalRelaycontrolsthestoplightsandwhichdirectional(turnsignal)lightsflashwhentheDirectionalSwitchissettoeitherrightorlefthandturn.TheEXUmodelshaddualrelays,oneforlefthandandoneforrighthand.ThemodernequivalentistheDB10EightPostDirectionalRelayunitcontrollingbothrightandlefthandturns.Originallytheseunitsweremechanical,thatis,theyusedcoiledrelaysliketheControlBox,buttoday’sversionisallsolid-state.Regardlessofmechanicalorsolid-state,itworksthesameway.Theonlyrealdifferenceisthatyoucannotrepairthesolid-stateversions,ifitgoesbadjustthrowitaway.Insidetheboxthereare:

• TwoMagneticCoils(A)• TwoMoveableArmature(B)• StopLightContacts(C),and• DirectionalLightContacts(D)

DirectionalRelayCircuitsPowerfortherelaycomesfromfourseparatesources:



• TheFlasher(1),• TheStopLightSwitch(5),• TheRightHandTurnDirectionalSwitch(4),and• TheLeftHandTurnDirectionalSwitch(8)

Allfouractindependently,andifoneshouldfail,theotherscancontinuetowork.Therearefouroutputs,

• TheRightFrontSideLight(2),• TheRightRearStop(D-Lamp)andSignalLight(3),• TheLeftHandFrontSideLight(6),and• TheLeftHandRearStop(D-Lamp)andSignalLight(7)

Note:FortherearStopandSignalLightconnections(3&7)thereisonlyonewireforboththeStopandSignalLights.ThusthesamewireisconnectedtoboththeStop(D-Lamp)andSignalLight.Becauseofthis,theStopLightandtheRearSignalLightsactasbothStopLightsandTurnSignalLights.WhenpowerenterstherelayfromtheDirectionalSwitchtoeitherconnection4or8,thecoilswoundaroundthecorrespondingironcorewillbecomemagnetized.ThismagnetwillthenpullitsmatchingMoveableArmature(B)awayfromits“atrest”state(shownintheabovediagram)andwillmakecontactwithboththeStopLight(C)andDirectionalLight(D)contacts(leftorright).Whencontactismade,thiswillcompletethecircuitfortheFlashertosendpowerthroughconnection1,acrosstheMoveableArmature(B)andouttoboththeFrontSideLamp(2or6)andStopandSignalLamps(3or7).Lookingatthediagramabove,youwillnoticethattheStopLightContacts(C)arealwaysconnectedregardlessofthepositionoftheMoveableArmature(B).WhentheTurnSignalsareactivated,andtheMoveableArmature(B)ismovedfromits“atrest”positiontosignalaturn,theStopLightdisconnectsfromtheStopLightSwitchpowerandreconnectstothenewcontactwithpowerfromtheFlasher.ThiswillcausetheStopLightonthatsideofthecartoblink.BasicallyturningitintoaDirectionalLight.TheStopLightfortheothersidewillstillcontinuetobepoweredfromtheStopLightSwitchandwillthusbehaveasa“normal”StopLight.



TheFlasherUnitTheFlasherUnitisasimpleelectro-mechanicaldevicethatturnsacircuitonandoffthroughtheuseofheat.Inthediagramtherearethreeconnections:

• B–forBattery• L–forLoad,and• P–forPanel

InsidetheFlasherthereistheTensionSpringBlade(1),aHeatingCoil(2)andtwosetsofContacts(3).WhentheDirectionalSwitchissettoeitherarightorlefthandturn,itcompletesacircuitfromA4oftheControlBoxtotheBconnectionthroughtheCoil(2)andouttheLconnectiontoaground.WhenthishappenstheCoilheatsup,whichthenheatstheTensionSpringBlade(1)causingittobendandbringingtheContacts(3)together.OncethisoccurstheelectricitywilltakethepathofleastresistancebypassingtheCoilsendingpowertoboththeLandPoutputs.TheseinturnwillsendpowertoboththeDirectionalSignalLights(L)andthebulbontheDirectionalSwitch(P).WithoutpowerthroughtheCoilitwillcoolwhichinturnallowstheTensionSpringBladetocoolresultinginitsnappingbackmakingaclickingsoundanddisconnectingtheContacts(3).ThepowerwillthenreturntotheCoil(2)andtheentirecyclerepeatsitselfyieldingtheclickingandblinkinglighteffect.



DirectionalIndicatorCircuitsPowerSource: Batteryand/orGeneratorIgnitionOnorOff: OnSwitchSettings: DirectionalSwitch: LeftorRightTurnand/or StopLightSwitch: BrakesAppliedThereareactuallythreeseparatebutintegratedcircuitsrepresentedinthisdiagram,onefortheStopLightsandtwofortheDirectionalLights.Asanote,thecolorschemefollowstheMGA,wheretheDB10wasfirstusedandnotthe“EXU”.TheStopLightsForthestoplights,powerbeginsattheA4connectionoftheRF95ControlBox,justasitdoesforthenormalStopLightcircuit.ItthencontinuestotheStopLightSwitch,butinsteadofgoingstraighttotheD-LampitattachestotheDirectionalRelayatconnection5.FromthereitflowsthroughtheRelayandoutconnections3and7totherightandlefthandD-LampsandrearTurnSignalLights.TheDirectionalLightsTheDirectionalLightsbeginsagainatA4ontheControlBox,thenontotheDirectionalSwitch.WhentheSwitchisturnedtoindicatearightorlefthandturn,powerexitstheswitchandconnectstotheDirectionalRelayat4forarighthandturnor8foralefthandturn.ThisresultsintheMoveableArmaturemovingandcompletingacircuitfortheFlasherunit,whichstartsatA4ontheControlBox,thentoconnectionBontheFlasherandoutbothconnectionLandP.ThePcircuitcontinuestotheDirectionalSwitchwhereitpowerstheindicatorlight.TheLcircuitenterstheRelayatconnection1whereitflowsthroughtherelayandoutboth6and7foralefthandturnor2and3forarighthandturn.



AppendixUsedWireNumberandColorsbyWireNumberYouwillnotethattheEarlyColorChartusedthewordingof“and”asin“Red&White”,whiletheRevisedsetuse“With”asin“Bluew/Red”.Notsureifthisismeaningfulornot. RevisedColors EarlyColorsNbr Color Nbr Color1 Blue 1 Red2 Bluew/Red 2 Red&Yellow4 Bluew/White 3 Red&Blue9 White 7 Red&Black16 Whitew/Black 8 Yellow17 Green 12 Yellow&Purple22 Greenw/Purple 13 Yellow&Black24 Greenw/Black 14 Blue25 Yellow 15 Blue&White29 Yelloww/Green 18 Blue&Purple33 Brown 20 White36 Brownw/Blue 22 White&Brown37 Brownw/White 23 White&Purple41 Red 24 White&Black42 Redw/Yellow 28 Green&Black44 Redw/White 31 Purple49 Purple 32 Purple&Black56 Purplew/Black 33 Black57 Black ThefollowingcolorsareusedbytheDB10DirectionalIndicatorsandhavenoequivalentsetuponearlierTC’s.Nbr Color14 Whitew/Purple15 Whitew/Brown18 Greenw/Red19 Greenw/Yellow20 Greenw/Blue21 Greenw/White23 Greenw/Brown



CrossReferenceofRevisedandEarlyUsedColorsThefirsttwocolumnsinthechartbelowarethewirecolorcodesandtheirnumbersshowninthewiringdiagramsabove.Thelasttwocolumnsaretheequivalentcolorsandnumbersusedbytheearlycarsforthosesamewires. RevisedColors EarlyColorEquivalentNbr Color Nbr Color1 Blue 15 Blue&White2 Bluew/Red 7 Red&Black4 Bluew/White 14 Blue9 White * 20 White16 Whitew/Black 22 White&Brown17 Green 32 Purple&Black22 Greenw/Purple # 31 Purple24 Greenw/Black 18 Blue&Purple25 Yellow * 8 Yellow29 Yelloww/Green 28 Green&Black33 Brown 13 Yellow&Black36 Brownw/Blue 24 White&Black37 Brownw/White 23 White&Purple41 Red * 1 Red42 Redw/Yellow * 2 Red&Yellow44 Redw/White 14 Blue49 Purple * 31 Purple56 Purplew/Black 12 Yellow&Purple57 Black * 33 Black*Thesecolorsactuallylineupoldtonew#PurplewasusedintheoldschemeforbothPurpleandGreenw/Purple

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