Toro Greensmaster 3120 - Page 215

Themainwiringharnesscontainssix(6)diodes.Thediodesareusedforcircuit
protectionfrominductivevoltagespikesandforsafetycircuitlogic.DiodesD1-A,
D1-B,D1-CandD1-Dareattachedtoacircuitboardthatplugsintothemain
wireharnesslocatedunderthecontrolpanelshield;refertoFigure95.Diodes
D2andD3areindividualplug-indiodesconnectedtothemainharnessnearthe
frontofthemowerhydraulicmanifold.
IdentifyingtheDiodesandtheirFunctions
DiodeD1-Aallowstheenginetostartonlywiththefunctioncontrolleverinthe
NEUTRALposition(neutralswitchclosed).Thediodealsoallowstheengineto
continuetorunwitheitherthefunctioncontrolleverintheNEUTRALpositionor
theoperatorsittingintheseat(seatswitchclosed).
DiodeD1-Bpreventsanegativevoltagespikefromdamagingtheneutralswitch
andseatswitchbyallowingapathtogroundforthestartsafetyrelay(K2)
whenitde-energizes.
DiodeD1-Cmaintainscurrentowtothejoystickrelay(K3)afterthejoystickis
releasedfromtheLOWERposition(joysticklowerswitchopens).
DiodeD1-Dpreventsanegativevoltagespikefromdamagingthemowand
backlapswitchesbyallowingapathtogroundforthemowrelay(K4)whenit
de-energizes.
DiodeD2preventscurrentowtosolenoidvalvecoilS4whensolenoidvalves
S2andS3areenergizedthroughbytheraiserelay(K6).
DiodeD3preventscurrentowtosolenoidvalvecoilS3whensolenoidvalves
S2andS4areenergizedthroughbythelowerrelay(K5).
TestingtheDiodes
1.Parkthemachineonalevelsurfaceandlowerthecuttingunits.Makesure
theengineisoffandthekeyswitchisintheOFFposition.
2.Accessthediodetobetestedanddisconnectthediodefromthemainwire
harness.
3.Useamultimeter(ohmssetting)andcheckthecontinuityacrossthediode
terminalsinbothdirections;refertotheDiodeT estingReference(page5–28).
Note:IfdiodesD1-A,D1-B,D1-CorD1-Daredamaged,theentirecircuit
boardshouldbereplaced.
4.Replacethediodeifnecessary.
5.Ifthediodetestscorrectlyandacircuitproblemstillexists,checkthewire
harnesses;refertoAppendixA(pageA–1).
Note:Applydielectricgeltothecircuitboardcontactswheneverthecircuit
boardisinstalledintothewireharness;refertoDielectricGel(page5–4).
6.Connectthediode(s)tothewireharnessbeforereturningthemachineto
service.
Greensmaster3120
Page5–29
ElectricalSystem:TestingtheElectricalComponents
17230SLRevC