Failure of the GPWC

TASK 34-48-00-810-801-A
Failure of the GPWC

1. Possible Causes

GPWC [1WZ]
short to ground at the wiring between the circuit breaker (3WZ) and the GPWC (1WZ)
C/B-EIS/GPWS/115VAC [3WZ]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 34-48-00-740-002	BITE Test of the GPWS
ASM 344801
AMM 34-48-34-000-001	Removal of the GPWC
AMM 34-48-34-400-001	Installation of the GPWC

3. Fault Confirmation
Subtask 34-48-00-865-050-A

A. Make sure that this(these) circuit breaker(s) is(are) closed:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
121VU	EIS/GPWS/115VAC	3WZ	P07

Subtask 34-48-00-740-050-C

B. Test
(1) If the circuit breaker (3WZ) trips, refer to Para. 4. C. of this trouble shooting procedure.
(2) Do the BITE test of the Enhanced GPWS AMM 34-48-00-740-002.

If the BITE test is not possible, refer to Para. 4. B. of this trouble shooting procedure.

4. Fault Isolation
Subtask 34-48-00-810-050-A

A. If the circuit breaker (3WZ) is closed, and if the BITE test gives the maintenance message GPWC (1WZ):

replace the GPWC [1WZ] AMM 34-48-34-000-001 and AMM 34-48-34-400-001.

Subtask 34-48-00-810-051-A

B. If the circuit breaker (3WZ) is closed and if the BITE test is not possible

do a check for 115VAC at pin AC/2 of the GPWC.

(1) If there is no 115VAC:

do a check of the wiring of the 115VAC signal from circuit breaker (3WZ) to GPWC (1WZ) ASM 344801.

(a) If there is no continuity:

repair the above wiring.

(b) If there is continuity:

replace the C/B-EIS/GPWS/115VAC (3WZ).

(2) If there is 115VAC:

do a check of the wiring of the ground signal at GPWC pin AC/3.

(a) If there is no continuity:

repair the above wiring.

Subtask 34-48-00-810-093-A

C. If the circuit breaker (3WZ) is open:

close this circuit breaker.

(1) If the circuit breaker (3WZ) trips:

remove the GPWC [1WZ] AMM 34-48-34-000-001.
close the circuit breaker (3WZ).

(a) If this circuit breaker stays closed:

install the GPWC AMM 34-48-34-400-001

1 If the circuit breaker trips again:

replace the GPWC AMM 34-48-34-000-001 and AMM 34-48-34-400-001.

(b) If this circuit breaker trips again:

do a check for a short to ground at the wiring between the circuit breaker (3WZ) and the GPWC (1WZ) ASM 344801.

1 If there is a short to ground:

repair the above wiring.

2 If there is no short to ground:

replace the C/B-EIS/GPWS/115VAC [3WZ] .

3 Install the GPWC
AMM 34-48-34-400-001.

Subtask 34-48-00-740-051-A

D. Do the test given in Para. 3.B.

[Rev.8 from Aug 2018] 2026.04.04 04:33:14 UTC