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(WARNING)
RED MESSAGE (CAUTION)
AMBER MESSAGE (ADVISORY)
CYAN MESSAGE (STATUS)
WHITE MESSAGE Require immediate crew attention. These messages are accompanied by flashing master warning, triple chime attenson with or without voice message or dedicated tone. Require immediate crew awareness and future crew action may be required in the form of alternate system selection or performance limitation. These message are accompanied by flashing master caution and a single chime. Indicate safe or normal system operation which require crew awareness, over and above the dark cockpit philosophy. Indicate minor failures or reduction in systems capability, which require no crew action.

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Quick Links

08/10/21

Message Overview:

Message Name:

AVIONICS RELAY FAILED
(Service Message)

Message Code:

B3-289404

Associated CAS:

None

Reporting LRU: AVIONICS VLV RLY
System Description: 21-23-00
Schematic Diagram: 21-23-00
Wiring Diagram: 21-23-01

Message Description:

The avionics relay K97 has been detected failed, by IASC1A and/or IASC2A.

Possible Causes:

  • Relay (K97) (JB3/DB2)
  • Integrated Air System Controller (IASC1) (A55)
  • Integrated Air System Controller (IASC2) (A56)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Relay K97 (and Relay K150) live inside JB3, on Card DB2. Power to K97 comes through K150 from two sources. IASC1A and IASC2A monitor the same "D" leg of relay K97. If the MDC fault is being reported by one IASC only, then suspect the IASC that is reporting the fault as they share the same bus.

Quick Links:

Removal of the Integrated Air System (IAS) Controller AMM 21-31-01-000-801
Installation of the Integrated Air System (IAS) Controller AMM 21-31-01-400-801
Removal of the Junction Box Circuit Cards AMM 24-63-05-000-802
Installation of the Junction Box Circuit Cards AMM 24-63-05-400-802
Removal of the Junction Box JB3 AMM 24-63-09-000-802
Installation of the Junction Box JB3 AMM 24-63-09-400-802
Standard Practices - Replace Wiring SPM 20-12-00-02
Standard Practices - Repair Wiring SPM 20-12-10-02

Troubleshooting Recommendations:

  1. Ensure the EMER DEPRESS PBA is not pushed in.
  2. Pull the circuit breakers CB5-B2 and CB6-B2.
  3. Disconnect A55P2 of the IASC1 and MPE14P1 of the avionics cooling valve.
  4. Do a continuity check between A55P1 Pin 19 and MPE14P1 Pin 3.

    1. If system checks are good, go step.
    2. If fault remains, continue with next step.

  5. Interchange IASCs.
  6. Replace the electronic card DB/JB3.
  7. Do close out.

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