The EXT PWR/AVAIL Caution Light and the AVAIL Legend of the ELEC/EXT PWR Pushbutton Switch Stay off when the EXT PWR Energizes the Aircraft

TASK 24-40-00-810-810-A
The EXT PWR/AVAIL Caution Light and the AVAIL Legend of the ELEC/EXT PWR Pushbutton Switch Stay off when the EXT PWR Energizes the Aircraft

1. Possible Causes

wiring
C/B-ELEC/EXT PWR/LT CLT/AVAIL [4XG]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 24-41-00-861-002	Energize the Aircraft Electrical Circuits from the External Power
AMM 24-41-00-862-002	De-energize the Aircraft Electrical Circuits Supplied from the External Power
ASM 244101

3. Fault Confirmation
Subtask 24-40-00-710-058-A ** ON A/C NOT FOR ALL

A. Test
(1) Energize the aircraft electrical circuits from the external power AMM 24-41-00-861-002

NOTE: Energization of the aircraft is correct but, during the procedure given at Para. 3.D., make sure that:

on the panel 108VU: the EXT PWR/NOT IN USE indicator light comes on and the EXT PWR/AVAIL caution light stays off.
on the panel 35VU: the AVAIL legend of the EXT PWR pushbutton switch stays off.

4. Fault Isolation
Subtask 24-40-00-810-059-A ** ON A/C NOT FOR ALL

A. If the test confirms the fault:

on the circuit breaker panel 122VU, do a check of the status of the circuit breaker (4XG).

(1) If the circuit breaker is closed:

do a check of the wiring between the pin 2 of the circuit breaker (4XG) and the first terminal block ASM 244101.

(a) If there is no continuity:

repair the above wiring.

(b) If there is continuity:

replace the C/B-ELEC/EXT PWR/LT CLT/AVAIL [4XG] .

(2) If the circuit breaker is open:

close it.

(a) If the circuit breaker trips:

do a check for a short to ground of the wiring which gets electrical power from the circuit breaker (4XG) ASM 244101.

1 If the wiring is not correct:

repair it.

2 If the wiring is correct:

replace the C/B-ELEC/EXT PWR/LT CLT/AVAIL [4XG] .

Subtask 24-40-00-710-059-A ** ON A/C NOT FOR ALL

B. Do this test to make sure that the system operates correctly:
(1) Do the test given in Para. 3. and make sure that:

on the panel 108VU, the EXT PWR/NOT IN USE indicator light and EXT PWR/AVAIL caution light come on
on the panel 35VU, the AVAIL legend of the EXT PWR pushbutton switch comes on.

(2) De-energize the aircraft electrical circuits from the external power AMM 24-41-00-862-002.

[Rev.8 from Aug 2018] 2026.04.04 04:26:53 UTC