TM 5-3805-262-20
3-24. ACCESSORIES TROUBLESHOOTING (CONT)
MALFUNCTION
TEST OR INSPECTION
CORRECTIVE ACTION
9. BOTH REAR DEFOGGER FANS DO NOT OPERATE (Cont).
Step 3.
Remove engine left side panels (page 9-14).
Connect multimeter across terminals of cab 30 ampere circuit
b r e a k e r.
3-174
Multimeter should indicate zero.
a. If multimeter indicates 24 volts, circuit breaker is open. Go to
step 4 below.
b. If multimeter indicates zero, replace cab relay (page 5-26).
Step 4.
Disconnect battery ground cable (page 5-148).
Disconnect wire connected between cab relay BAT. terminal and cab 30
ampere circuit breaker long, silver terminal.
Reconnect battery ground cable.
Connect multimeter between long, silver terminal of cab 30 ampere
circuit breaker and chassis .
Multimeter shall indicate 24 volts.
a. If multimeter indicates zero, replace cab 30 ampere circuit
breaker (page 5-26).
b. If multimeter indicates 24 volts, a short circuit to ground
e 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 by
reconnecting wire from cab relay BAT. terminal to long, silver
terminal of cab circuit breaker. Then, at cab switch panel,
disconnect and tape wires connected to each of the three circuit
breakers one at a-time and check if remaining circuit(s) operate
when associated switch is operated.
