W DOC AIRBUS | TSM A320F

Loss of the HMU Control through the two Channels on Engine 2

TASK 73-29-00-810-841-A
Loss of the HMU Control through the two Channels on Engine 2

1. Possible Causes
2. Job Set-up Information
 A. Referenced Information
REFERENCE
DESIGNATION
AMM 73-21-10-000-001
Removal of the Hydromechanical Unit (HMU)
AMM 73-21-10-400-001
Installation of the Hydromechanical Unit (HMU)
AMM 73-21-50-000-006
Removal of J7 Harness
AMM 73-21-50-000-007
Removal of J8 Harness
AMM 73-21-50-400-006
Installation of the J7 Harness
AMM 73-21-50-400-007
Installation of the J8 Harness
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)
ASM 732518
AMM 73-29-00-710-040
Operational Test of the FADEC on the ground (with Engine Motoring)
3. Fault Confirmation
Subtask 73-29-00-710-098-A ** ON A/C NOT FOR ALL
A. Test
   (1) Do the operational test of the FADEC 2A and 2B on the ground (with engine motoring) AMM 73-29-00-710-040.
   (2) Read the TROUBLE SHOOTING DATA of the FADEC MENU on the MCDU (Ref. 70-00-00, P. Block 301).
4. Fault Isolation
Subtask 73-29-00-810-101-A ** ON A/C NOT FOR ALL
A. If the test gives the maintenance messages J7, HMU, ECU + J8, HMU, ECU and the TROUBLE SHOOTING DATA gives the complementary information HPT TORQUE MOTOR CURRENT:
  • do a check for open or short to ground at pins J7/10, 23, 24 and J8/10, 23, 24 of the harnesses J7 and J8 from the ECU (4000KS) to the HPT torque-motor current in theHMU ASM 732518.
   (1) If one of these wirings is not correct:
  • repair the defective harness J7 or J8.
   (2) If these wirings are correct:
  • disconnect the harnesses J7 and J8 from the ECU and do a check of the ECU cable resistance between:
    . pins 23 and 24 (17 to 23 Ohms)
    . pins 23 and 10 (> 10 Megohms)
    . pin 23 and the ground (> 10 Megohms).
     (a) If the resistance values are in the specified limits:
     (b) If the resistance values are out of the specified limits:
  • disconnect the harnesses J7 and J8 from the HMU and do a resistance check of the HMU between:
    . pins 23 and 24 (17 to 23 Ohms)
    . pins 23 and 10 (> 10 Megohms)
    . pin 23 and the ground (> 10 Megohms).
       1 If the resistance values are in the specified limits:
       2 If the resistance values are out of the specified limits:
Subtask 73-29-00-810-102-A ** ON A/C NOT FOR ALL
B. If the test gives the maintenance messages J7, HMU, ECU + J8, HMU, ECU and the TROUBLE SHOOTING DATA gives the complementary information BSV SOLENOID CURRENT:
  • do a check for open or short to ground at pins J7/6, 7, 39 and J8/6, 7, 39 of the harnesses J7 and J8 from the ECU (4000KS) to the BSV solenoid current in the HMU ASM 732518.
   (1) If one of these wirings is not correct:
  • repair the defective harness J7 or J8.
   (2) If these wirings are correct:
  • disconnect the harnesses J7 and J8 from the ECU and do a check of the ECU cable resistance between:
    . pins 6 and 7 (26 to 36 Ohms)
    . pins 6 and 39 (> 10 Megohms)
    . pin 6 and the ground (> 10 Megohms).
     (a) If the resistance values are in the specified limits:
     (b) If the resistance values are out of the specified limits:
  • disconnect the harnesses J7 and J8 from the HMU and do a resistance check of the HMU between:
    . pins 6 and 7 (26 to 36 Ohms)
    . pins 6 and 39 (> 10 Megohms)
    . pin 6 and the ground (> 10 Megohms).
       1 If the resistance values are in the specified limits:
       2 If the resistance values are out of the specified limits:
Subtask 73-29-00-810-103-A ** ON A/C NOT FOR ALL
C. If the test gives the maintenance messages J7, HMU, ECU + J8, HMU, ECU and the TROUBLE SHOOTING DATA gives the complementary information RAC TORQUE MOTOR CURRENT:
  • do a check for open or short to ground at pins J7/20, 39, 40 and J8/20, 39, 40 of the harnesses J7 and J8 from the ECU (4000KS) to the RACC torque motor in the HMU ASM 732518.
   (1) If one of these wirings is not correct:
  • repair the defective harness J7 or J8.
   (2) If these wirings are correct:
  • disconnect the harnesses J7 and J8 from the ECU and do a check of the ECU cable resistance between:
    . pins 20 and 40 (17 to 23 Ohms)
    . pins 20 and 39 (> 10 Megohms)
    . pin 20 and the ground (> 10 Megohms).
     (a) If the resistance values are in the specified limits:
     (b) If the resistance values are out of the specified limits:
  • disconnect the harnesses J7 and J8 from the HMU and do a resistance check of the HMU between:
    . pins 20 and 40 (17 to 23 Ohms)
    . pins 20 and 39 (> 10 Megohms)
    . pin 20 and the ground (> 10 Megohms).
       1 If the resistance values are in the specified limits:
       2 If the resistance values are out of the specified limits:
Subtask 73-29-00-810-213-A ** ON A/C NOT FOR ALL
D. If the test gives the maintenance message J7, HMU, ECU + J8, HMU, ECU and the TROUBLE SHOOTING DATA gives the complementary information LPT TORQUE MOTOR CURRENT:
  • do a check for open or short to ground at pins J7/19, 38, 39 and J8/19, 38,39 of the harnesses J7 and J8 from the ECU (4000KS) to the LPT torque-motor current in the HMU ASM 732518.
   (1) If the wiring is not correct:
  • repair the defective harness J7 or J8.
   (2) If the wiring is correct:
  • disconnect the harnesses J7 and J8 from the ECU and do a check of the ECU cable resistance between:
    . pins 19 and 38 (17 to 23 Ohms)
    . pins 19 and 39 (> 10 Megohms)
    . pin 19 and the ground (> 10 Megohms).
     (a) If the resistance values are in the specified limits:
     (b) If the resistance values are out of the specified limits:
  • disconnect the harnesses J7 and J8 from the HMU and do a resistance check of the HMU between:
    . pins 19 and 38 (17 to 23 Ohms)
    . pins 19 and 39 (> 10 Megohms)
    . pin 19 and the ground (> 10 Megohms).
       1 If the resistance values are in the specified limits:
       2 If the resistance values are out of the specified limits:
Subtask 73-29-00-710-099-A ** ON A/C NOT FOR ALL
E. Do the test given in Para. 3.A.(1).
[Rev.8 from Aug 2018] 2026.04.04 04:35:56 UTC
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