W DOC AIRBUS | TSM A320F

Loss of the Leak Detection Loop of the APU

TASK 36-22-00-810-868-A
Loss of the Leak Detection Loop of the APU

1. Possible Causes
  • BMC-1 [1HA1]
  • wiring
  • sensing element
2. Job Set-up Information
 A. Referenced Information
REFERENCE
DESIGNATION
AMM 36-11-00-740-802
BITE Test of the Engine Bleed Air System (EBAS) (System Test)
AMM 36-11-34-000-001
Removal of the BMC
AMM 36-11-34-400-001
Installation of the BMC
ASM 362201
AMM 36-22-17-000-001
Removal of the APU Overheat Sensing-Elements
AMM 36-22-17-400-001
Installation of the APU Overheat Sensing-Elements
3. Fault Confirmation
Subtask 36-22-00-710-113-A ** ON A/C NOT FOR ALL
A. Test
   (1) Do the BITE test of the EBAS AMM 36-11-00-740-802.
4. Fault Isolation
Subtask 36-22-00-810-135-A ** ON A/C NOT FOR ALL
A. If the test gives the maintenance message:
APU LOOP INOP:
NOTE: This procedure is related to the loss of the APU-loop detection signal or to incorrect continuity of the loop.
The resistance of the loop must be less than 15 Ohms at ambient temperature.
The BMC gives the maintenance message when the resistance of the loop is more than 75 Ohms (discontinuity).
There is continuity when the resistance of the loop is less than 75 Ohms.
   (1) If there is continuity:
  • Do a check for a ground signal at pin AA/4C of BMC1 ASM 362201.
     (a) If there is no ground signal:
     (b) If there is a ground signal:
       1 If the fault continues and the resistance of the loop is between 15 Ohms and 75 Ohms:
  • Do a check and clean all the connections to remove contamination and decrease the resistance of the loop.
   (2) If there is no continuity:
  • Do a check of the wiring from pin AA/4C of BMC1 to the cable (11HF) and from pin AA/5C of BMC1 to the cable (20HF) ASM 362201.
     (a) If there is no continuity:
     (b) If there is continuity:
  • Do a visual inspection of the sensing elements on the APU loop.
       1 If a sensing element is damaged:
       2 If no sensing element is damaged:
  • Do a continuity check of each sensing element, one after the other.
    * Connecting cable (11HF)
    * Sensing element (12HF)
    * Sensing element (13HF)
    * Sensing element (14HF)
    * Sensing element (15HF)
    * Sensing element (16HF)
    * Sensing element (17HF)
    * Sensing element (18HF)
    * Sensing element (19HF)
    * Connecting cable (20HF).
         a If there is no continuity on a sensing element:
         b If there is continuity on all the sensing elements:
  • Do a check and repair the wiring from pin AA/4C to the sensing element (12HF) ASM 362201.
  • Do a check and repair the wiring from the sensing element (19HF) to pin AA/5C ASM 362201.
  • Install BMC-1 [1HA1] AMM 36-11-34-400-001.
Subtask 36-22-00-710-114-A ** ON A/C NOT FOR ALL
B. Do the test given in Para. 3.
[Rev.8 from Aug 2018] 2026.04.04 04:34:09 UTC
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