Message Name:

INTERNAL FAULT
(Service Message)

Message Code:

B3-006755

Associated CAS:

None

Internal fault to the FIREX Control Unit has been detected.

• FIREX Control Unit (A91)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

During aircraft power-up, if the aircraft left essential bus (L BATT) is depressed first, the right essential bus (R BATT) will power up approximately 700 milliseconds later. This threshold value may be close enough to upset the FIREX control unit microprocessor delay time to monitoring the discrete. The microprocessor is being fed from the left essential bus, whereas the output discretes circuits are being powered from the right essential bus.

1. Check and reset FIREX Control Unit (A91) circuit breaker CB5-A3, CB6-A4 in DCPC.

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

2. Check and reset Fire Detector circuit breakers CB2-A11 (R BATT) and then CB1-A11 (L BATT).

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

3. Perform wiring check between FIREX control unit and circuit breakers and ground. (repair as required).

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

4. Replace FIREX control unit.
5. Do close out.