CAB, CHASSIS, AND TRAILER WIRING SYSTEMSSUB-SYSTEMSSlide 3Slide 4Slide 5WIRING STANDARDSElectrical MapsCIRCUIT IDENTIFICATIONHARNESS STANDARDSOTHER HARNESS STANDARDSCAB, CHASSIS, AND TRAILER WIRING SYSTEMSSUB-SYSTEMSMain Cab Harness•Receives power from Batteries•Has Fuses and Circuit Breakers•Feeds power to other truck harnesses•Extends to cab/front lighting on some cab designs• Some fuse panels identified wellSUB-SYSTEMSEngine Harness•Supplies power to starter motor, alternator, Jacob engine brake, preheating/starting system, fan clutch, shutterstats and heating and air conditioning system•Supplies power to Chassis Harness on some trucksSUB-SYSTEMSChassis Harness•Supplies power to all frame mounted electrical and electronic components such as;•lighting•anti-skid brakes•fuel tank level gauge•trailer coupling connectorSUB-SYSTEMSTrailer Harness•Supplies power to lighting on the trailer(s)WIRING STANDARDSAmerican Manufactuers follow SAE and TMC/ATA standardsWiring diagram supplied with every truck (affixed or pouch)Circuit identification is standardWiring ColorsStandard nomenclature or abbreviationsElectrical MapsWiring Diagram•Grid Reference System•Pages identified by model of truckCircuit Diagram•Shows how components are connected together without detail•Specifies location of wiring and componentsCIRCUIT IDENTIFICATIONTwo Methods•Color and Number•Circuit Number and Circuit NameLetters and Numbers can be printed on wiring every 4 inchesWiring can be taggedFIG 5-3HARNESS STANDARDSWIRE CONDUCTORS•ANNEALED COPPER WIREWIRE INSULATION•SXL - Standard duty thermosetting cross-linked polyethylene•Wiring temp must not exceed 100 degree F•If higher temp, must be protectedOTHER HARNESS STANDARDSVoltage drop not more than 0.5VMust be supported at least every 18 inchesWiring Harness CoveringsWiring should be located so that rocks, road debris, etc will not harm