Removal of the Avionics-Ventilation Blower and Extract Fan Pressure-Switches

TASK 21-26-11-000-001-A
Removal of the Avionics-Ventilation Blower and Extract Fan Pressure-Switches

ZONE: 121
ZONE: 125
ZONE: 127
ZONE: 128
FIN: 17HQ
FIN: 19HQ
FIN: 30HQ

1. Reason for the Job
Self explanatory
2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	1	ACCESS PLATFORM 2M (6 FT) - ADJUSTABLE
No specific	AR	CAP - BLANKING
No specific	AR	PLUG - BLANKING
No specific	AR	SAFETY CLIP - CIRCUIT BREAKER

B. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
121	AVIONICS COMPARTMENT
125	LATERAL AVIONIC COMPARTMENT
127	REAR AVIONIC COMPARTMENT
128	REAR AVIONIC COMPARTMENT
811, 824
FOR [17HQ] (PRESS SW-BLOWER FAN, AVNCS VENT)
811
FOR [19HQ] (PRESS SW-BLOWER FAN, AVNCS VENT)
824
FOR [30HQ] (PRESS SW-EXTRACT FAN, AVNCS VENT)
824

C. Referenced Information

REFERENCE	DESIGNATION
TASK 24-42-00-861-001-A	Energize the Ground Service Network from the External Power
Avionics-Ventilation Blower-Fan Pressure-Switches ** ON A/C NOT FOR ALL
Avionics-Ventilation Extract-Fan Pressure-Switch
Avionics-Ventilation Blower-Fan Pressure-Switches ** ON A/C NOT FOR ALL
FOR [17HQ] (PRESS SW-BLOWER FAN, AVNCS VENT)
TASK 52-41-00-010-002-A	Open the Avionics Compartment Doors for Access
FOR [19HQ] (PRESS SW-BLOWER FAN, AVNCS VENT)
TASK 52-41-00-010-002-A	Open the Avionics Compartment Doors for Access
FOR [30HQ] (PRESS SW-EXTRACT FAN, AVNCS VENT)
TASK 52-41-00-010-002-A	Open the Avionics Compartment Doors for Access

3. Job Set-up
Subtask 21-26-11-861-050-A

A. Energize the ground service network (Ref. AMM TASK 24-42-00-861-001).

Subtask 21-26-11-010-050-A

B. Get Access
(1) Put the ACCESS PLATFORM 2M (6 FT) - ADJUSTABLE in position at access doors 811 and 824.
(2) Open the access doors that follow:
(a) FOR [17HQ] (PRESS SW-BLOWER FAN, AVNCS VENT)

811 (Ref. AMM TASK 52-41-00-010-002).

(b) FOR [19HQ] (PRESS SW-BLOWER FAN, AVNCS VENT)

824 (Ref. AMM TASK 52-41-00-010-002).

824 (Ref. AMM TASK 52-41-00-010-002).

Subtask 21-26-11-865-050-A

C. Open, safety and tag this(these) circuit breaker(s):

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
FOR FIN: 19HQ (PRESS SWBLOWER FAN, AVNCS VENT) FOR FIN: 17HQ (PRESS SWBLOWER FAN, AVNCS VENT)
49VU	AIR COND/AVNCS VENT/CTL	6HQ	D06
49VU	AIR COND/AVNCS VENT/CTL	5HQ	D05
122VU	AIR COND/AVNCS/VENT/MONG	3HQ	Y17
123VU	AVNCS VENT/BLOWER/FAN	1HQ	AD10
FOR FIN: 30HQ (PRESS SWEXTRACT FAN, AVNCS VENT)
49VU	AIR COND/AVNCS VENT/CTL	6HQ	D06
49VU	AIR COND/AVNCS VENT/CTL	5HQ	D05
** 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

4. Procedure
Subtask 21-26-11-020-052-A

A. Removal of the Avionics-Ventilation Extract-Fan Pressure-Switch
(1) Make match marks on the components that you disconnect/remove to record their connections/positions. This is important for the subsequent installation procedure.

CAUTION: MAKE SURE THAT THE ELECTRICAL CONNECTORS ARE CLEAN BEFORE YOU DISCONNECT OR CONNECT THEM. CONTAMINATION ON THE ELECTRICAL CONNECTORS CAN CAUSE DAMAGE TO EQUIPMENT.

(2) Disconnect the electrical connector (9) as follows:
(a) Disconnect the electrical connector (9) from the avionics-ventilation extract-fan pressure-switch (8).
(b) Put the CAP-BLANKING on each disconnected electrical connector and receptacle.
(3) Disconnect the pipe (4) from the reducer (3).
(4) Remove the reducer (3) from the avionics-ventilation extract-fan pressure-switch (8).
(5) Remove the blanking cap (5) from the avionics-ventilation extract-fan pressure-switch (8).
(6) Put the PLUG-BLANKING in each disconnected line end.
(7) Hold the avionics-ventilation extract-fan pressure-switch (8) and remove the screws (6) and the washers (7).
(8) Remove the avionics-ventilation extract-fan pressure-switch (8) from its support (1).
(9) Remove the O-ring (2) and discard it.

Subtask 21-26-11-020-051-A

B. Removal of the Avionics-Ventilation Blower-Fan Pressure-Switch
(1) Make match marks on the components that you disconnect/remove to record their connections/positions. This is important for the subsequent installation procedure.

CAUTION: MAKE SURE THAT THE ELECTRICAL CONNECTORS ARE CLEAN BEFORE YOU DISCONNECT OR CONNECT THEM. CONTAMINATION ON THE ELECTRICAL CONNECTORS CAN CAUSE DAMAGE TO EQUIPMENT.

(2) Disconnect the electrical connector (1) as follows:
(a) Disconnect the electrical connector (1) from the avionics-ventilation blower-fan pressure-switch (2).
(b) Put the CAP-BLANKING on each disconnected electrical connector and receptacle.
(3) Disconnect the pipe (7).
(4) Remove the blanking cap (8) from the reducer (6).
(5) Remove the reducer (6) from the avionics-ventilation blower-fan pressure-switch (2).
(6) Put the PLUG-BLANKING in each disconnected line end.
(7) Hold the avionics-ventilation blower-fan pressure-switch (2) and remove the screws (4) and the washers (3).
(8) Remove the avionics-ventilation blower-fan pressure-switch (2) from its support.
(9) Remove the O-ring (5) and discard it.

[Rev.10 from 2021] 2026.04.02 06:11:02 UTC