TM 1-1520-238-T-4
4–138
Change 1
4–53.
EMERG PWR INDICATOR – IS NOT LIGHTED WITH CKT B SWITCH SET TO ENG 1 (cont)
4–53
7. Check for open between:
P175–15 and P748–Z,
P175–14 and P748–Y.
(A78):
K1–3 and J1–12,
J1–14 and J1–15.
Does open exist?
YES
Repair open wire.
Go to paragraph 4–12.
NO
Go to step 8.
8. Check for open between:
P21–4 and P41–5,
P21–5 and P41–7.
Does open exist?
YES
(ABY) Repair open wire.
Go to paragraph 4–12.
(ABZ) Replace wire harness
(TM 1-1520-238-23).
NO
Go to step 9.
9. Check for open between:
J21–4 and P175–3,
J21–5 and P175–1.
Does open exist?
YES
Repair open wire.
Go to paragraph 4–12.
NO
Go to step 10.
10. Check for 18 to 28 VDC between P175–3 and
P175–1.
Is voltage present?
YES
Go to step 12.
NO
Go to step 11.
11. Check for 115 VAC between P41–1 and P41–2.
Is voltage present?
YES
Refer to TM 55-2840-248-23 to
troubleshoot engine 2, (ABY)
ECU.
(ABZ) DECU.
NO
Go to step 13.
12. Check for open between P175–12 and P748–a.
Does open exist?
YES
Repair open wire.
Go to paragraph 4–12.
NO
Replace multi–channel dimming
controller (TM 1-1520-238-23).
13. Check for 115 VAC at P1–22.
Is voltage present?
YES
Go to step 14.
NO
Refer to TM 1-1520-238-T-6 to
troubleshoot circuit protection
system (ac essential bus 1
–pilot station).
14. Check for open between:
P21–1 and P41–1,
P21–2 and P41–2.
Does open exist?
YES
(ABY) Repair open wire.
Go to paragraph 4–12.
(ABZ) Replace wire harness
(TM 1-1520-238-23).
NO
Go to step 15.
15. Check for open between:
(A402)J1–22 and J21–1
(A402)GS9–M and J21–2.
Does open exist?
YES
Repair open wire.
Go to paragraph 4–12.
NO
Refer to TM 55-2840-248-23 to
troubleshoot engine 1, (ABY)
ECU.
(ABZ) DECU.
END OF TASK
