Message Name:

UNABLE TO POWER THE AIRCRAFT WHILE DCPC FAN IS HEARD ACTIVE

With no external power applied to the aircraft and Battery (BATT) MASTER Switch set to OFF, the DC Power Center (DCPC) Fan can be heard running. When attempting to apply power to the aircraft, the power distribution system fails to respond. The aircraft remains unpowered.

• Auxiliary Power Unit (APU) Start Contactor Assembly (ASCA) (A48)
• DC Power Center (DCPC) (A63)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Full Throttle Blog/Forum Articles/Infoservice/Newsletter: None

Flight Operation Notifications Manual (FONM): None

1. While you can hear the DCPC fan running, even though aircraft power is OFF, disconnect the APU Battery. Check if the DCPC fan running sound still be heard.

   1. If NO, go to step 7.
   2. If YES, continue with next step.

2. Reconnect the APU Battery and disconnect the Avionics Battery to confirm the DCPC fan stops running.
3. Reconnect the Avionics Battery and access the DCPC.
4. One at a time, pull the circuit breakers on the DCPC to the 'OUT' position until you can hear the fan stop.
5. Record what system the circuit breaker is feeding and troubleshoot that system and perform a wiring check.

   1. If wiring checks are not good, repair defective wiring as required and go to step 11.
   2. If wiring checks are good, continue with next step.

6. Reconnect the APU Battery.
   NOTE: You may need a second person and means of communication for the following steps.
7. Access the ASCA.
8. One at a time, pull the circuit breakers on the ASCA to the 'OUT' position until you can hear the fan stop.
9. Record what system the circuit breaker is feeding and troubleshoot that system and defective wiring. Repair/rectify as required and continue with next step.
10. In order to clear a possible latched DCPC fault, you will need to perform the DCPC Virgin Start Procedure.
11. Only once the Virgin Start procedure has been performed, apply power to the aircraft and make sure everything is functioning as it should.
    NOTE: Some circuit breakers may have been set to 'OUT' when the system had failed. You may need to check status of all the circuit breakers and make sure the aircraft is configured correctly.
12. Make sure a detailed description of the fault is indicated on the MRA of the faulty LRU if applicable.
13. Do close out.