The EXT PWR/AVAIL Caution Light Stays off when the EXT PWR Energizes the Aircraft

TASK 24-40-00-810-808-A
The EXT PWR/AVAIL Caution Light Stays off when the EXT PWR Energizes the Aircraft

1. Possible Causes

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 24-40-00-710-054-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 comes on.

4. Fault Isolation
Subtask 24-40-00-810-057-A ** ON A/C NOT FOR ALL

A. If the test confirms the fault:

on the panel 108VU, push the LIGHT TEST pushbutton switch (34LP) to do a test of the lights of the panel 108VU.

(1) If the EXT PWR/AVAIL caution light comes on:

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:

(b) If there is continuity:

(2) If the EXT PWR/AVAIL caution light stays off:

(a) If the fault continues:

do a check of the wiring :
. between the pin 23 of the diode module (1191VD) and the first terminal block
. between the pin 2 of the caution light and the pin 8 of the diode module (1191VD)
. between the pins 1 and 4 of the caution light
. between the pin 5 of the caution light and the first terminal block ASM 244101..

1 If there is no continuity:

2 If there is continuity:

Subtask 24-40-00-710-055-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 04:26:52 UTC