Lycoming TEO-540-C1A Maintenance Manual page 522

Fault ID 336
Fault
Power box power source fault
Description
This fault indicates the average engine speed is consistently above the calibrated maximum
engine speed to switch to PMA power source however AIRFRAME is still the Power Box
Root Cause
power source. The fault is raised possibly due to a Power Box failure or Cam/crank sensor
failure
1. Are there any active crankshaft or camshaft sensor faults? If yes, proceed to fault troubleshooting for
that fault(s). If no, go to step 2.
2. Gain access to engine rear accessory drive area, and inspect the following items:
•
PMA for obvious damage and security.
•
Engine harness for obvious damage and security, including harness PMA connector.
Are the PMA and engine harness secure and show no physical damage? If yes, go to step 3.
If no, complete the following for the finding:
•
PMA not secure.
o Remove PMA per the "PMA Removal" section in Chapter 73-10 and inspect PMA shaft and
gear for damage. If damage is found, replace the PMA, and inspect accessory gear drive for
damage. If no damage is found on either the PMA or accessory gear drive, reinstall PMA per
the "PMA Installation" section in Chapter 73-10.
•
PMA damaged. Replace the PMA per the "Permanent Magnet Alternator (PMA) Replacement"
section in Chapter 73-10.
•
Engine harness damaged. Contact Lycoming Engines.
3. Complete a continuity and short circuit test of the engine and engine airframe harnesses from PMA
connector to the Power Box connector using the engine system schematic. If the continuity or short
circuit check fails, isolate to affected harness by disconnecting the engine harness at the firewall
connector, then contact Lycoming Engines. If both checks pass, replace the Power Box. Is fault still
active? If yes, contact Lycoming Engines. If no, go to step 4.
4. Clear Service faults using the FST by following the steps outlined in the "Access the Field Service
Tool" section in Appendix C or the latest revision of SSP-118.
Appendix D
Page 492
Fault Group 43
Troubleshooting Steps
TEO-540-C1A Engine Maintenance Manual
Fault Name
[FAULT: APU power source cutoff]
Fault Lamp
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NTO
November 2018