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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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02/26/21

Message Overview:

Message Name:

CROSSWIRED LOOPS

Message Code:

B3-008135

Associated CAS:

FIRE SYS FAULT
(Advisory)

Reporting LRU: APU FIRE LOOPS
System Description: 26-13-00
Schematic Diagram: 26-13-00
Wiring Diagram: 26-13-01

Message Description:

A and B fire detection loops on the APU are cross-wired.

Possible Causes:

  • Auxiliary Power Unit (APU) Fire Detection Elements are crossed
  • Fire-Detection and Extinguishing (FIREX) Control Unit (CU) (A91)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Quick Links:

Removal of the Fire-Detection-and-Extinguishing (FIREX) Control-Unit AMM 26-11-01-000-801
Installation of the Fire-Detection-and-Extinguishing (FIREX) Control-Unit AMM 26-11-01-400-801
Removal of the Eductor Sensing Element AMM 26-13-01-000-801
Installation of the Eductor Sensing Element AMM 26-13-01-400-801
Removal of the Firewall Sensing Element AMM 26-13-05-000-801
Installation of the Firewall Sensing Element AMM 26-13-05-400-801
Kiddie Aerospace CMM 26-11-88
Electrical Bonding - Adjustment/Test SPM 51-80-00-05
Wiring - Maintenance Practices - ALL SPM 20-12-00-02
Wire Repair - Maintenance Practices - ALL SPM 20-12-10-02

Troubleshooting Recommendations:

  1. Pull and reset FIREX Control Unit (A91) circuit breaker CB2-A11, CB6-A4. Recheck MDC for the fault.

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

  2. Do LDE checks on FIREX APU Loop A, If loops do not ring out, gain access to the loops and correct the wiring segments assuring that the firewall A103 loop A is matched with Eductor A104 loop A, firewall A105 loop B is matched with eductor A106 loop B. Check the individual segments back to the FIREX control.

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

  3. Perform the electrical bonding test.

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

  4. Replace FIREX CU.
  5. Do close out.

21_firex_cu_install60_rh_cbpnl13_apu_firewall_detection_harness60_rh_dcpc_cb_panel

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