Incorrect Readout of the Standby Altimeter

TASK 34-21-00-810-801-A
Incorrect Readout of the Standby Altimeter

1. Possible Causes

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 32-31-71-000-001	Removal of the LGCIU
AMM 32-31-71-400-001	Installation of the LGCIU
ASM 326201
ASM 342101
AMM 34-21-22-000-001	Removal of the Standby Altimeter
AMM 34-21-22-400-001	Installation of the Standby Altimeter

3. Fault Confirmation
Subtask 34-21-00-865-050-A ** ON A/C NOT FOR ALL

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

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C NOT FOR ALL
49VU	NAV/STBY/ALTM	16FN	F14

Subtask 34-21-00-710-050-A ** ON A/C NOT FOR ALL

B. Test
(1) Not applicable, the fault is evident.

4. Fault Isolation
Subtask 34-21-00-810-050-A ** ON A/C NOT FOR ALL

A. If the movement of the pointer is not correct:

disconnect connector A of the standby altimeter (3FN)
connect a voltmeter between pins A and D of the standby altimeter connector and make sure that the voltmeter readout is equal to O V.

(1) If the voltmeter readout is equal to O V:

disconnect then connect connector AB of the LGCIU1 (5GA1) and make sure that the voltmeter readout changes from O V to 28VDC and then to O V.

(a) If the voltmeter readout is correct:

(b) If the voltmeter readout is not correct:

1 If the fault continues:

do a check of the wiring of the relay (11GB):
. from pin A/A2 to the circuit breaker (16FN)
. from pin A/A3 to the standby altimeter (3FN)
ASM 342101.

a If there is no continuity:

b If there is continuity:

(2) If the voltmeter readout is not equal to O V:

(a) If the fault continues:

1 If the fault continues:

do a check and repair the wiring from the LGCIU1 (5GA1) to the SYS1 L/G position relay (11GB): from pin AB/1B to pin A/X2 ASM 326201.

[Rev.8 from Aug 2018] 2026.04.04 04:32:55 UTC