TM 5-3805-262-203-24. ACCESSORIES TROUBLESHOOTING (CONT)MALFUNCTIONTEST OR INSPECTIONCORRECTIVE ACTION8. DEFROSTER MOTOR DOES NOT OPERATE (Cont).Step 4.Step 5.Step 6.Disconnect battery ground cable (page 5-148).Disconnect wire connected between cab relay BAT. terminal and cab 30ampere circuit breaker long, silver terminal.Reconnect battery ground cable.Connect multimeter between long, silver terminal of cab 30 amperec i r c u i t b r e a k e r a n d c h a s s i s .Multimeter shall indicate 24 volts.a. If multimeter indicates zero, replace cab 30 ampere circuitbreaker (page 5-26).b. If multimeter indicates 24 volts, a short circuit to grounde x i s t s i n c a b e l e c t r i c a l c i r c u i t . I s o l a t e d e f e c t i v e c i r c u i t byr e c o n n e c t i n g w i r e f r o m c a b r e l a y B A T . t e r m i n a l t o l o n g , s i l v erterminal of cab circuit breaker. Then , at cab switch panel, dis-connect and tape wires connected to each of the three circuitbreakers one at a time and check if remaining circuit(s) operatewhen associated switch is operated. If circuit is okay, problemis in circuit associated with breaker from which wire was dis-connected.Press 6 ampere circuit breaker on cab switch panel.Check if defroster motor operates.a. If defroster motor operates, problem was momentary short inc i r c u i t .b . I f c i r c u i t b r e a k e r b l o w s , a short to ground exists in circuit.Go to step 6 below.c. If defroster motor does notoperate, go to step 7 below.Turn ignition key switch to offp o s i t i o n.Remove HEAT CONTROL knob fromcab switch panel by pullings t r a i g h t u p o f f c o n t r o l s h a f t.Remove four screws securing cabswitch panel.3-171
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