Fault Message:

OPEN CKT - EGT SENSOR/CKT 1 WIRING

Fault Code:

4960149APU

Associated CAS:

APU FAULT
(Advisory)

The Exhaust Gas Temperature (EGT) Sensor 1 conditioning voltage in the Full Authority Digital Engine Control (FADEC) is out of range low and the signal read by the FADEC is out of range low. This shows a possible open in the EGT Sensor or wiring. This fault is shown when EGT Sensor 2 is not failed.

• Exhaust-Gas Temperature (EGT) Sensor (TC1)
• Auxiliary Power Unit (APU) Full-Authority Digital Engine-Controller (FADEC) (A108)
• Associated Wiring

Advisory Wire/Service Bulletin: None

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If CAS message is not active, verify stored faults on CAIMS, under System Diagnostics, ATA 49 (this will include ground and air faults).

1. Visually inspect the EGT Sensors for signs of water that would cause a short between the posts. Use Honeywell SIL-APU-87 if needed to add more RTV.
2. Inspect the wiring and connectors to the EGT sensor 1 for any damage, repair or replace as required.

   1. If there is any damage, repair or replace as required and do close out.
   2. If there is no damage, continue with next step.

3. Inspect the EGT sensor 1 for condition and check that the resistance between the Alumel and Chromel terminal as follows:

   From	To	Expected Result	Result
   Alumel	Chromel	<20 ohms

   1. If there is any damage, replace the EGT sensor 1 and do close out.
   2. If there is no damage, continue with next step.

4. Re-rack FADEC and verify connector A108BP1-K6 and A108BP1-K5 for damage or FOD. Verify if fault is still present?

   1. If YES, repair defective wiring as required and do close out.
   2. If NO, continue with next step.

5. Perform wiring checks between APU firewall connector (P802) and the EGT sensor 1 as follow:

   From	To	Expected Result	Result
   P802-11	Chromel	<6 ohms
   P802-12	Alumel	<6 ohms

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

6. Perform wiring checks between APU firewall connector (J802) the APU FADEC connector (A108BP1).

   From	To	Expected Result	Result
   J802-11	A108BP1-K6	<11 ohms
   J802-12	A108BP1-K5	<11 ohms

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

7. Replace APU FADEC.
8. Do close out.