Loss of the FMV Torque Motor Control through the Channel A on Engine 2

TASK 73-29-00-810-870-A
Loss of the FMV Torque Motor Control through the Channel A on Engine 2

1. Possible Causes

ECU [4000KS]
HMU-2 [4000KC2]
harness J7

2. Job Set-up Information
A. Referenced Information

REFERENCE	DESIGNATION
AMM 73-21-10-000-001	Removal of the Hydromechanical Unit (HMU)
AMM 73-21-10-000-002	Removal of the Hydromechanical Unit (HMU)
AMM 73-21-10-400-001	Installation of the Hydromechanical Unit (HMU)
AMM 73-21-10-400-002	Installation of the Hydromechanical Unit (HMU)
AMM 73-21-50-000-006	Removal of J7 Harness
AMM 73-21-50-000-040	Removal of the HJ7 Harness for SAC Engines
AMM 73-21-50-210-001	Visual Inspection of the Wiring Harness
AMM 73-21-50-210-002	Visual Inspection of the Wiring Harnesses
AMM 73-21-50-400-006	Installation of the J7 Harness
AMM 73-21-50-400-040	Installation of the HJ7 Harness for SAC Engines
AMM 73-21-60-000-001	Removal of the Electronic Control Unit (ECU)
AMM 73-21-60-400-001	Installation of the Electronic Control Unit (ECU)
AMM 73-29-00-710-040	Operational Test of the FADEC on the ground (with Engine Motoring)

3. Fault Confirmation
Subtask 73-29-00-710-156-A ** ON A/C NOT FOR ALL

A. Test
(1) Do the operational test of the FADEC 2A on the ground (with engine non - motoring) AMM 73-29-00-710-040.

4. Fault Isolation
Subtask 73-29-00-810-162-A ** ON A/C NOT FOR ALL

A. Do this procedure:

NOTE: This fault is generated if there is an open or short to ground in the torque motor current loop on channel A.

(1) If the test does not give the maintenance message J7, HMU(FMV TM), ECU:

No maintenance action is required.

(2) If the test does not give the maintenance message J7, HMU(FMV TM), ECU, but is repetitive:

replace the ECU [4000KS] , AMM 73-21-60-000-001 and AMM 73-21-60-400-001.

(a) If the fault continues during the subsequent flights:

replace the HMU-2 [4000KC2] AMM 73-21-10-000-001 and AMM 73-21-10-400-001.

1 If the fault continues during the subsequent flights:

replace the harness J7 , AMM 73-21-50-000-006 and AMM 73-21-50-400-006.

(3) If the test gives the maintenance message J7, HMU(FMV TM), ECU:

Disconnect the J7 harness from the ECU (4000KS) receptacle and visually examine it and the J7 harness connector for damaged pins, contamination AMM 73-21-50-210-001.

(a) If damage on a connector is found:

Replace or repair as required.

(b) If nothing is found:

Do an electrical resistance test through the J7 harness between:
. pins 27 and 28 (17 to 23 Ohms)
. pins 27 and 12 (> 10 Megohms)
. pin 27 and the ground (> 10 Megohms).

1 If the resistance values are in the specified limits:

replace the ECU [4000KS] , AMM 73-21-60-000-001 and AMM 73-21-60-400-001.

2 If the resistance values are out of the specified limits:

Reconnect the J7 harness to the ECU (4000KS) receptacle, and continue the troubleshooting.

(c) Disconnect the J7 harness from the HMU receptacle (HMU-A) (located left hand core compartment), and visually examine the J7 harness connector and the HMU receptacle for damaged pins, contamination and fuel wetting AMM 73-21-50-210-001.
1 If damage on a connector is found:

Replace or repair as required.

2 If fuel wetting is found:

replace the harness J7 , AMM 73-21-50-000-006 and AMM 73-21-50-400-006.

3 If nothing is found:

Do an electrical resistance test on the HMU receptacle between:
. pins 27 and 28 (17 to 23 Ohms)
. pins 27 and 12 (> 10 Megohms)
. pin 27 and the ground (> 10 Megohms).

a If the resistance values are in the specified limits:

replace the harness J7 , AMM 73-21-50-000-006 and AMM 73-21-50-400-006.

b If the resistance values are out of the specified limits:

replace the HMU-2 [4000KC2] AMM 73-21-10-000-001 and AMM 73-21-10-400-001.

Subtask 73-29-00-810-162-B ** ON A/C NOT FOR ALL