TM 5-5420-234-14&P
4-12. UNIT TROUBLESHOOTING (continued).
6.
INDICATOR/PANEL LIGHTS DO NOT OPERATE (MODEL A ONLY) (continued).
3.
TEST OPTIONS
KNOWN INFO
Relay K4 Test.
Circuit breaker OK.
Is LED D7 on the cab
Supply harness OK.
control box circuit
REASON FOR QUESTION
board illuminated?
POSSIBLE PROBLEMS
If LED D7 is lit, power is
reaching the relay and
Control box circuit board
the relay is defective. If
faulty.
LED D7 is not lit, the
Relay no. K4 faulty.
cab control box circuit
board is faulty.
Replace cab
NO
control box circuit
board (para 4-71).
Replace relay K4
YES
4-118
Change 1
