Fault Message:

HIGH OIL TEMPERATURE

Fault Code:

4960124APU

Associated CAS:

APU OIL HI TEMP
(Caution)

APU SHUTDOWN
(Advisory)

This Engine Indication and Crew Alerting System (EICAS) message is shown when the oil temperature of the Auxiliary Power Unit (APU) is more than 300 °F (148.9 °C) for ten seconds while the aircraft is in the air, or during a main engine start sequence.

• Auxiliary Power Unit (APU) Air Inlet Door
• Air/Oil Cooler Duct
• Oil Temperature Sensor (MT6)
• Oil Cooler Thermostatic/Pressure Relief Valve
• Auxiliary Power Unit (APU) Full Authority Digital Engine (Electronic) Control (FADEC)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

NOTE: If CAS message is not active, verify stored flight faults on CAIMS, under system diagnostics, ATA 49.The Thermostatic/ Pressure Relief Valve is normally a non field replaceable item. It will be included in the Oil Cooler Assy.

1. Visually check the oil quantity in the APU.

   1. If APU oil level was low, investigate absence of APU OIL LO QTY, CAS
      (Advisory) message.
   2. If system checks are good, do close out.
   3. If fault remains, continue with next step.

2. On CAIMS verify if fault FADEC CONTROLLER is active.

   1. If active, continue with next step.
   2. If fault FADEC CONTROLLER is still active, replace the FADEC and do close out.
   3. If the FADEC CONTROLLER is not active, go to step 4.

3. Rerack the FADEC and verify connector A108BP1, pins B-G6, B-H6 and B-J6 for damage or FOD.

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.

4. Verify that the APU air intake inlet door opens fully per AMM TASK 49-14-01-710-801 (Do not start the APU, put the APU control panel knob in the run position only and verify door position visually and on APU DATA status page).

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.

5. Inspect the air inlet duct and oil cooler for FOD or signs of blockage.

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.

6. Measure the oil temperature and cross-check resistance value between pin A and B of the oil temperature sensor (MT6P1).

   ºC	Ohms Resistance	ºC	Ohms Resistance
   -70	68.27 ±0.50	60	112.28 ±0.50
   -60	71.19 ±0.50	70	116.27 ±0.50
   -50	74.24 ±0.40	80	120.36 ±0.50
   -40	77.39 ±0.40	90	124.55 ±0.50
   -30	80.56 ±0.40	100	128.85 ±0.50
   -20	83.77 ±0.40	110	133.26 ±0.50
   -10	87.04 ±0.40	120	137.78 ±0.60
   	90.38 ±0.40	130	142.40 ±0.60
   10	93.80 ±0.40	140	147.11 ±0.60
   20	97.31 ±0.40	150	151.91 ±0.60
   30	100.91 ±0.40	200	177.95 ±1.00
   40	104.60 ±0.40	250	208.00 ±1.00
   50	108.39 ±0.40	300	242.70 ±1.50

   1. If measurements are out of range, Replace the oil temperature sensor and do close out.
   2. If measurements are good, continue with next step.

7. Perform wiring checks between APU FADEC and the oil temperature sensor connector (MT6P1).

   1. If wiring checks are not good, repair defective wiring as required and do close out.
   2. If wiring checks are good, continue with next step.

8. Replace the oil cooler assy (includes thermostatic/pressure relief valve as part of the assy).

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.

9. Replace the APU FADEC.
10. Do Close out.