Failure of the Extract Fan

TASK 21-26-00-810-810-A
Failure of the Extract Fan

1. Possible Causes

CNTOR-EXTRACT FAN CTL, AVNCS VENT (7HQ)
FAN-EXTRACT, AVNCS VENT [18HQ]
C/B-AVNCS VENT/EXTC/FAN [2HQ]
AEVC [10HQ]
wiring
C/B-AIR COND/AVNCS VENT/CTL [6HQ]
PRESS SW-EXTRACT FAN, AVNCS VENT [30HQ]

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
TSM TASK 24-00-00-810-803-A	Circuit Breaker Tripped and/or C/B TRIPPED Warning
AMM 21-26-00-710-001	Operational Check of the Avionics Equipment Ventilation-System via MCDU
AMM 21-26-00-710-008	Operational Test to Read the CFDS for CLASS 3 Faults of the AEVC
AMM 21-26-00-710-009	Operational Test to Read the CFDS for LAST LEG REPORT of the AEVC
ASM 212602
AMM 21-26-11-000-001	Removal of the Blower and Extract Fan Pressure Switches
AMM 21-26-11-400-001	Installation of the Blower and Extract Fan Pressure Switches
AMM 21-26-34-000-001	Removal of the Avionics Equipment Ventilation Computer (AEVC)
AMM 21-26-34-400-001	Installation of the Avionics Equipment Ventilation Computer (AEVC)
AMM 21-26-51-000-001	Removal of the Extract and Blower Fans
AMM 21-26-51-400-001	Installation of the Extract and Blower Fans

3. Fault Confirmation
Subtask 21-26-00-865-054-A

A. Table of the circuit breakers used in this procedure:

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
49VU	AIR COND/AVNCS VENT/CTL	6HQ	D06
122VU	AIR COND/AVNCS/VENT/MONG	3HQ	Y17
** ON A/C NOT FOR ALL
123VU	AVNCS VENT/EXTC/FAN	2HQ	AE02
** ON A/C NOT FOR ALL
123VU	AVNCS VENT/EXTC/FAN	2HQ	AC04

Subtask 21-26-00-710-092-B

B. Test
(1) Do the reset of the AEVC (10HQ).
(a) Open the circuit breaker AIR COND/AVNCS/VENT/MONG (3HQ).
(b) Wait for five seconds.
(c) Close the circuit breaker AIR COND/AVNCS/VENT/MONG (3HQ).
(2) Do the operational test of the avionics equipment ventilation from the Multipurpose Control and Display Unit (MCDU) AMM 21-26-00-710-001.
(3) Read the LAST LEG REPORT AMM 21-26-00-710-009.
(4) Read the CLASS 3 faults of the AEVC AMM 21-26-00-710-008.

4. Fault Isolation
Subtask 21-26-00-810-073-A

A. If the test gives the maintenance message EXTRACT FAN 18HQ:
(1) If the AVNCS VENT/EXTC/FAN circuit breaker (2HQ) is open:

Do the procedure (Ref. TSM TASK 24-00-00-810-803).

(a) If the fault continues:

Replace the CNTOR-EXTRACT FAN CTL, AVNCS VENT (7HQ).

(b) If the fault continues:

Replace the FAN-EXTRACT, AVNCS VENT [18HQ] AMM 21-26-51-000-001 and AMM 21-26-51-400-001.

Replace the C/B-AVNCS VENT/EXTC/FAN [2HQ] .

(2) If the fault continues:

Replace the AEVC [10HQ] AMM 21-26-34-000-001 and AMM 21-26-34-400-001.

(3) If the fault continues:

Do a check of the status of the AVNCS VENT/EXTC/FAN circuit breaker (2HQ).

(4) If the AVNCS VENT/EXTC/FAN circuit breaker (2HQ) is closed:

Do a check for 115VAC at pins A/J, A/K, A/L of the extract fan (18HQ).

(a) If there is no 115VAC:

Do a check for 115VAC at pins T1, T2, T3 of the extract-fan control contactor (7HQ).

1 If there is no 115VAC:

Do a check of the wiring ASM 212602 between the extract-fan control contactor (7HQ) pins L1, L2, L3 and the AVNCS VENT/EXTC/FAN circuit breaker (2HQ) pins A2, B2, C2.

a If the wiring is not correct:

Repair the related wiring.

b If the wiring is correct:

Replace the C/B-AVNCS VENT/EXTC/FAN [2HQ] .

2 If there is 115VAC:

Do a check of the status of the AIR COND/AVNCS VENT/CTL circuit breaker (6HQ).

a If the AIR COND/AVNCS VENT/CTL circuit breaker (6HQ) is closed:

Do a check for 28VDC at pin A/E of the extract fan (18HQ).

* If there is no 28VDC:
* - Do a check of the wiring ASM 212602 between:
* . The extract fan (18HQ) pin A/E and the AIR COND/AVNCS VENT/CTL circuit breaker (6HQ)
* . The extract fan (18HQ) pin A/F and the ground.

** If the wiring is not correct:
** - Repair the related wiring.

** If the wiring is correct:
** - Replace the C/B-AIR COND/AVNCS VENT/CTL [6HQ] .

* If there is 28VDC:
* - Make sure that the warning light of the extract fan (18HQ) is off.

** If the warning light is on, push the RESET pushbutton switch on the extract fan (18HQ).

NOTE: The fan starts immediately.
The warning light goes off.

** If the fault continues:
** - Replace the FAN-EXTRACT, AVNCS VENT [18HQ] AMM 21-26-51-000-001 and AMM 21-26-51-400-001.

** If the fault continues:
** - Do a check for 28VDC at pin AA/9A of the AEVC (10HQ) ASM 212602.

*** If there is 28VDC:
*** - Replace the AEVC [10HQ] AMM 21-26-34-000-001 and AMM 21-26-34-400-001.

*** If there is no 28VDC:
*** - Do a check of the wiring ASM 212602 between:
*** . The AEVC (10HQ), pin AA/9A and the extract-fan control contactor (7HQ), pin Z
*** . The extract-fan control contactor (7HQ), pin X and the extract fan (18HQ), pin A/D.

**** If the wiring is not correct:
**** - Repair the related wiring.

**** If the wiring is correct:
**** - Replace the CNTOR-EXTRACT FAN CTL, AVNCS VENT (7HQ).

**** If the fault continues:
**** - Replace the FAN-EXTRACT, AVNCS VENT [18HQ] AMM 21-26-51-000-001 and AMM 21-26-51-400-001.
b If the AIR COND/AVNCS VENT/CTL circuit breaker (6HQ) is open:

Do the procedure (Ref. TSM TASK 24-00-00-810-803).

* If the fault continues:
* - Replace the C/B-AIR COND/AVNCS VENT/CTL [6HQ] .

(b) If there is 115VAC:

Replace the FAN-EXTRACT, AVNCS VENT [18HQ] AMM 21-26-51-000-001 and AMM 21-26-51-400-001.

(5) If the fault continues:

Replace the PRESS SW-EXTRACT FAN, AVNCS VENT [30HQ] AMM 21-26-11-000-001 and AMM 21-26-11-400-001.

Subtask 21-26-00-710-093-A

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

[Rev.8 from Aug 2018] 2026.04.04 04:24:37 UTC