APU Audible Surge (131-9(A))

TASK 49-00-81-810-906-A
APU Audible Surge (131-9(A))

1. Possible Causes

APU air inlet
wiring
Surge Control Valve (8058KM)
Delta Pressure Sensor (8043KM)
Total Pressure Sensor (8044KM)
APU [4005KM]

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

REFERENCE	QTY	DESIGNATION
No specific	1	MULTIMETER - STANDARD

B. Referenced Information

REFERENCE	DESIGNATION
AMM 49-11-11-000-004	Removal of the Power Plant (APU) (131-9(A))
AMM 49-11-11-400-004	Installation of the Power Plant (APU) (131-9(A))
AMM 49-16-00-210-802	General Visual Inspection of APU Air Inlet Plenum and APU Air Intake (131-9(A))
AMM 49-16-42-000-003	Removal of the Air Intake Duct (131-9(A))
AMM 49-16-42-400-003	Installation of the Air Intake Duct (131-9(A))
AMM 49-20-00-200-003	APU Power Plant Borescope Inspection (131-9(A))
AMM 49-20-00-210-003	APU Power Plant Visual Inspection (Honeywell 131-9 (A))
AMM 49-51-16-000-002	Removal of the Transducer - Differential Pressure (131-9(A))
AMM 49-51-16-400-002	Installation of the Transducer - Differential Pressure (131-9(A))
AMM 49-51-17-000-002	Removal of the Transducer - Total Pressure (131-9(A))
AMM 49-51-17-400-002	Installation of the Transducer - Total Pressure (131-9(A))
AMM 49-51-52-000-003	Removal of the Surge Control Valve (131-9(A))
AMM 49-51-52-400-003	Installation of the Surge Control Valve (131-9(A))
ASM 732509

3. Fault Confirmation
Subtask 49-00-81-710-264-A ** ON A/C NOT FOR ALL

A. Not applicable

4. Fault Isolation
Subtask 49-00-81-810-193-A ** ON A/C NOT FOR ALL

A. If there is an APU audible surge:
(1) Check the CFDS for fault messages.
(a) If a fault message shows:

Do the related troubleshooting procedure.

(b) If no fault message shows:
1 Do a visual inspection of the APU air inlet for airflow blockage, FOD/DOD, plenum splitter loose and/or detachments AMM 49-16-00-210-802.
2 Do a visual inspection of the air flow sensors and tubes. Do a check for signs of blockage or leakage AMM 49-16-00-210-802.
3 If necessary, repair and/or replace AMM 49-16-42-000-003 AMM 49-16-42-400-003.

Subtask 49-00-81-810-194-A ** ON A/C NOT FOR ALL

B. If the fault continues:
(1) Do a check and repair the wiring from EIU-1 (1KS1) to the ECB (59KD), pin AB/1C to pin AB/E5 ASM 732509.

Subtask 49-00-81-810-205-A ** ON A/C NOT FOR ALL

C. If the fault continues:
(1) Do a check for damage/contamination of electrical connector P18 of the Surge Control Valve.
(a) If the electrical connector P18 is damaged/contaminated:

Do a repair/cleaning of the connector P18.

(b) If the electrical connector P18 is in correct condition:
1 Use a MULTIMETER - STANDARD to do a resistance check across
pin 1 and pin 2
pin 2 and pin 3
pin 4 and pin 5
of the Surge Control Valve connector P18.

If the resistance check shows OPEN (>1MOhm) or SHORT (<500 mOhms) circuit, replace the Surge Control Valve (8058KM) AMM 49-51-52-000-003 AMM 49-51-52-400-003.

Subtask 49-00-81-810-206-A ** ON A/C NOT FOR ALL

D. If the fault continues:
(1) Do an inspection of the Delta Pressure Sensor.

If necessary, replace the Delta Pressure Sensor (8043KM) AMM 49-51-16-000-002 AMM 49-51-16-400-002.

(2) Do an inspection of the Total Pressure Sensor.

If necessary, replace the Total Pressure Sensor (8044KM) AMM 49-51-17-000-002 AMM 49-51-17-400-002.

Subtask 49-00-81-810-207-A ** ON A/C NOT FOR ALL

E. If the fault continues:
(1) Do an inspection of the IGVs, including mechanical linkage, and IGV actuators AMM 49-20-00-210-003.

Subtask 49-00-81-810-208-A ** ON A/C NOT FOR ALL

F. If the fault continues:
(1) Do a borescope inspection of the Load Compressor Impeller AMM 49-20-00-200-003.

Subtask 49-00-81-810-209-A ** ON A/C NOT FOR ALL

G. If the fault continues:
(1) Replace the APU [4005KM] AMM 49-11-11-000-004 AMM 49-11-11-400-004.

[Rev.8 from Aug 2018] 2026.04.04 04:34:39 UTC