Removal of the AC Essential Bus Switching Contactor

TASK 24-25-55-000-001-A
Removal of the AC Essential Bus Switching Contactor

WARNING: MAKE SURE THAT NO AC OR DC POWER IS CONNECTED TO THE AIRCRAFT ELECTRICAL CIRCUITS. THERE IS A RISK OF ELECTROCUTION IF THE AC OR DC POWER STAYS CONNECTED.

ZONE: 125
FIN: 3XC

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	SAFETY CLIP - CIRCUIT BREAKER

B. Work Zones and Access Panels

ZONE/ACCESS	ZONE DESCRIPTION
125	LATERAL AVIONIC COMPARTMENT
812

C. Referenced Information

REFERENCE	DESIGNATION
Contactor

3. Job Set-up
Subtask 24-25-55-941-051-A

A. Safety Precautions
(1) In the cockpit, on the overhead panel 35VU, make sure these pushbutton switches are released:

BAT 1, BAT 2,
GEN 1, GEN 2,
EXT A.

(2) In the cockpit, put a warning notice to tell persons not to operate the pushbutton switches on these panels of the overhead panels:

35VU (ELEC),
21VU (EMER ELEC PWR).

(3) Make sure that the external power connector is not connected to the aircraft receptable EXT PWR A.
(4) Put a warning notice on the access door 121AL to tell persons not to connect the external power connector.

Subtask 24-25-55-010-050-A

B. Get access to the avionics compartment.
(1) Put an ACCESS PLATFORM 2M (6 FT) - ADJUSTABLE in position at the access door 812.
(2) Open the access door 812.
(3) Remove the access door (14) from the panel 106VU.

Subtask 24-25-55-865-052-A

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

PANEL	DESIGNATION	FIN	LOCATION
** ON A/C ALL
105VU	ELEC/CSM/G /EV AUTO/SPLY	7XE	C01
106VU	CSM/G /EV/MAN/SPLY	6XE	B04
106VU	ESS TR/SPLY	4PE	C01
122VU	ELEC/CNTOR/ESS/DC BUS/TIE	3PC	W26
123VU	AC ESS/BUS ON/BUS 1	1XC	AC12
123VU	AC ESS/BUS ON/BUS 2	2XC	AC01

4. Procedure
Subtask 24-25-55-020-050-A

A. Removal of the Contactor
(1) Disconnect the two electrical connectors (1, 2).
(2) Put CAP - BLANKING on the electrical connectors (1, 2) and the electrical receptacles (12, 13)
(3) Loosen the 9 nuts (3).
(4) Remove the 9 nuts (3), the spring washers (4) and the plates (5) and (10).
(5) Remove the electrical wires:

CAUTION: MAKE MATCH MARKS ON ALL THE ELECTRICAL WIRES BEFORE YOU DISCONNECT THEM. INCORRECT CONNECTION OF WIRES WILL CAUSE DAMAGE TO EQUIPMENT.

(a) Remove the electrical power supply wires (6).
(6) Loosen the 4 nuts (7).
(7) Hold the contactor (8).
(8) Remove the 4 nuts (7) and the washers (9).
(9) Remove the contactor (8).

[Rev.10 from 2021] 2026.03.31 23:22:50 UTC