Buffer Air Valve Solenoid Electrical Failure Channel B

TASK 75-26-04-810-802-A
Buffer Air Valve Solenoid Electrical Failure Channel B

1. Possible Causes

BUFFER AIR VALVE SOLENOID [4056KS]
W03 HARNESS [4087KS]
W04 HARNESS [4088KS]
WC08 HARNESS-CORE [4094KS]
[4000KS]

2. Job Set-up Information
A. Fixtures, Tools, Test and Support Equipment

REFERENCE	QTY	DESIGNATION
No specific	1	MULTIMETER - STANDARD
No specific	1	PLIERS - JAWED, SOFT

B. Referenced Information

REFERENCE	DESIGNATION
TSM TASK 71-00-00-810-834-A	General Troubleshooting Guidelines for Additional Troubleshooting Information
TSM TASK 71-00-00-810-835-A	Component and Harness Intermittent Troubleshooting Procedure for Guidance Troubleshooting Intermittent Faults
AMM 70-70-00-910-803	SPOP 6 - Cleaning of the Contact Points and Wiring Harnesses
AMM 73-21-00-710-806	Test No.7 - EEC Operation Test (Self Test)
AMM 73-21-01-000-801	Removal of the Electronic Engine Control (EEC)
AMM 73-21-01-400-801	Installation of the Electronic Engine Control (EEC)
AMM 73-21-63-000-802	Removal of the Electronic Engine Control (EEC) Wiring Harness (W03)
AMM 73-21-63-400-802	Installation of the Electronic Engine Control (EEC) Wiring Harness (W03)
AMM 73-21-64-000-802	Removal of the Electronic Engine Control (EEC) Wiring Harness (W04)
AMM 73-21-64-400-802	Installation of the Electronic Engine Control (EEC) Wiring Harness (W04)
AMM 73-21-68-000-802	Removal of the EEC Wiring Harness (WC08)
AMM 73-21-68-400-802	Installation of the EEC Wiring Harness (WC08)
AMM 75-26-04-000-801	Removal of the Buffer Air Valve Solenoid
AMM 75-26-04-400-801	Installation of the Buffer Air Valve Solenoid
AMM 78-36-00-010-802	Opening of the Thrust Reverser Cowl-Doors
AMM 78-36-00-410-802	Closing of the Thrust Reverser Cowl-Doors
EEC Wiring Harnesses
W04/WC08 Interconnect Wiring Harness
Buffer Air Valve Solenoid Wiring Harness
Buffer Air Valve Solenoid Wiring Schematic
W03/W04 Interconnect Wiring Harness

3. Fault Confirmation
Subtask 75-26-04-710-051-A ** ON A/C NOT FOR ALL

A. Do the EEC system interactive test to confirm this fault. Refer to FADEC self test AMM 73-21-00-710-806.

NOTE: The Electronic Engine Control (EEC) has detected the circuit for the buffer air valve solenoid is open or shorted in channel B. The buffer air valve solenoid is on the compressor intermediate case, located at the 3 o'clock position.

Refer to the general troubleshooting guidelines for additional troubleshooting information (Ref. TSM TASK 71-00-00-810-834).
Refer to the component and harness intermittent troubleshooting procedure for guidance troubleshooting intermittent faults (Ref. TSM TASK 71-00-00-810-835).

(1) If the maintenance message does not come back, examine the harnesses and electrical connectors as described in the component and harness intermittent fault isolation procedure (Ref. TSM TASK 71-00-00-810-835).
(a) If no problems are found, return the engine to service. Monitor the engine for reoccurring maintenance message.
(2) If the maintenance message comes back (hard fault), go to the Para. Fault Isolation.

4. Fault Isolation

WARNING: BE CAREFUL WHEN YOU DO WORK ON THE ENGINE AFTER SHUTDOWN. THE ENGINE CAN STAY HOT FOR A LONG TIME. IF YOU DO NOT OBEY THIS WARNING, INJURY CAN OCCUR.

WARNING: REFER TO THE MSDS FOR ALL MATERIAL USED AND THE MANUFACTURER'S SAFETY INSTRUCTIONS FOR ALL EQUIPMENT USED. IF YOU DO NOT OBEY THIS WARNING, INJURY CAN OCCUR.

CAUTION: MAKE SURE YOU REMOVE ELECTRICAL POWER FROM THE EEC BEFORE YOU REMOVE THE ELECTRICAL CONNECTORS. IF YOU DO NOT OBEY THIS INSTRUCTION, DAMAGE TO THE EEC CAN OCCUR.

Subtask 75-26-04-810-051-A ** ON A/C NOT FOR ALL

A. If there is confirmation of the fault:
(1) Open the thrust reverser cowl-doors AMM 78-36-00-010-802.
(2) Examine the W03 (4087KS), W04 (4088KS) and WC08 (4094KS) harnesses and connector P4 (4000KS-P4) - EEC (4000KS), interconnect P107 (4101VC-A)/J107 (4101VC), interconnect J109 (4112VC)/P109 (4112VC-A) and connector P21 (4056KS-P21) - buffer air valve solenoid (4056KS), for problems which are possible between the EEC (4000KS) and the buffer air valve solenoid (4056KS).
(a) Inspect for harness damage.
(b) Inspect for loose or damaged connectors.

NOTE: Loose connectors must be disconnected and examined for further wear or damage.

(c) If a problem is found with the harness or connectors:
1 Replace W03 HARNESS(4087KS) AMM 73-21-63-000-802 and AMM 73-21-63-400-802, or
2 Replace W04 HARNESS(4088KS) AMM 73-21-64-000-802 and AMM 73-21-64-400-802, or
3 Replace WC08 HARNESS-CORE(4094KS) AMM 73-21-68-000-802 and AMM 73-21-68-400-802.
4 Do the test given in Para. 3.
(3) If no problems are found with the harness, use a PLIERS - JAWED, SOFT to disconnect electrical connector P4 (4000KS-P4) from the EEC (4000KS), interconnect P107 (4101VC-A)/J107 (4101VC), interconnect J109 (4112VC)/P109 (4112VC-A) and connector P21 (4056KS-P21) from the buffer air valve solenoid (4056KS).
(a) Examine the pins and sockets (contacts) for alignment and damage. Look for contacts pushed rearward into the connector face. Replace parts as necessary.
(b) Clean the contacts with contact cleaner and clean cloth per SPOP 6. Blow dry with air (at less than 30 psi) across the connector face AMM 70-70-00-910-803.
(c) Reconnect electrical connector P4 (4000KS-P4) to the EEC (4000KS), interconnect P107 (4101VC-A)/J107 (4101VC), interconnect J109 (4112VC)/P109 (4112VC-A) and connector P21 (4056KS-P21) to the buffer air valve solenoid (4056KS).
(d) Do the test given in Para. 3.
(4) If the fault continues:
(a) Replace BUFFER AIR VALVE SOLENOID [4056KS] AMM 75-26-04-000-801 and AMM 75-26-04-400-801.
(b) Do the test given in Para. 3.
(5) If the fault continues:
(a) Disconnect electrical connector P4 (4000KS-P4) from the EEC (4000KS), interconnect P107 (4101VC-A)/J107 (4101VC), interconnect J109 (4112VC)/P109 (4112VC-A) and connector P21 (4056KS-P21) from the buffer air valve solenoid (4056KS). Use a MULTIMETER - STANDARD to test the buffer air valve solenoid (4056KS) circuits in the harnesses. Refer to Table 1. Look for:
1 Wire-to-wire shorts
2 Shorts to ground
3 Continuity (less than 5 ohms resistance).

NOTE: A short to ground is found when the resistance is less than 100 000 (100K) ohms.

Table 1: Buffer Air Valve Solenoid Channel B Connector Contacts

W03 (4087KS) Harness P4 (4000KS-P4) EEC(4000KS) Connector Contacts	W03 (4087KS) Harness P107 (4101VC-A) Connector Contacts	W04 (4088KS) Harness J107 (4101VC) Connector Contacts	W04 (4088KS) Harness J109 (4112VC) Connector Contacts	WC08(4094KS) Harness P109 (4112VC-A) Connector Contacts	WC08(4094KS) Harness P21 (4056KS-P21) Buffer Air Valve Solenoid (4056KS) Connector Contacts
CC	13	13	14	14	4
DD	29	29	15	15	3

(b) If a problem is found with the harnesses or connectors:
1 Replace W03 HARNESS [4087KS] AMM 73-21-63-000-802 and AMM 73-21-63-400-802, or
2 Replace W04 HARNESS [4088KS] AMM 73-21-64-000-802 and AMM 73-21-64-400-802, or
3 Replace WC08 HARNESS-CORE [4094KS] AMM 73-21-68-000-802 and AMM 73-21-68-400-802.
4 Do the test given in Para. 3.
(6) If the fault continues:
(a) Replace [4000KS] AMM 73-21-01-000-801 and AMM 73-21-01-400-801.
(b) Do the test given in Para. 3.

5. Close-up
Subtask 75-26-04-860-051-A ** ON A/C NOT FOR ALL

A. Put the aircraft back to its initial configuration.
(1) Make sure that the work area is clean and clear of tools and other items.
(a) Close the thrust reverser cowl-doors AMM 78-36-00-410-802.

[Rev.8 from Aug 2018] 2026.04.04 04:37:19 UTC