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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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02/23/21

Message Overview:

Message Name:

NO L-VHF-3 BUS OUTPUT

Message Code:

B3-008077

Associated CAS:

None

Reporting LRU: VHF 1
System Description: 23-11-00
Schematic Diagram: 23-11-00
Wiring Diagram: 23-11-01

Message Description:

Left VHF is not transmitting ARINC data to L-RIU.

Possible Causes:

  • Left VHF Communication Unit (VHF 1) (A7)
  • Left Radio Interface Unit (RIU 1) (A17)
  • COM 1 Circuit Breaker (CB1-B2)
  • Left Circuit Breaker Panel (CBP1)
  • Associated Wiring

Troubleshooting Tips:

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

Quick Links:

Removal of the VHF Communication Unit AMM 23-11-01-000-801
Installation of the VHF Communication Unit AMM 23-11-01-400-801
Removal of the Radio Interface Unit (RIU) AMM 23-51-21-000-801
Installation of the Radio Interface Unit (RIU) AMM 23-51-21-400-801
Replacement of DC Circuit Breakers AMM 24-65-00-960-801
Removal of the Cockpit Circuit Breaker Panel (CCBP) AMM 24-65-01-000-801
Installation of the Cockpit Circuit Breaker Panel (CCBP) AMM 24-65-01-400-801
Standard Practices - Replace Wiring SPM 20-12-00-02
Standard Practices - Wire Repair SPM 20-12-10-02

Troubleshooting Recommendations:

  1. Reset COM 1 Circuit Breaker CB1-B2. Is the fault message still present?

    1. If YES, continue with next step.
    2. If NO, do close out.

  2. Swap left VHF (A7) with right VHF (A8). Is the fault message still present?

    1. If YES, continue with next step.
    2. If NO, replace defective VHF.

  3. Swap left RIU (A17) with right RIU (A18). Is the fault message still present?

    1. If YES, continue with next step.
    2. If NO, replace defective RIU.

  4. Do wiring check between left VHF (A7) and left RUI (A17) for the following wires:

    From To Result
    Conn. A7P1 - 17 Conn. A17P1 - 17
    Conn. A7P1 - 18 Conn. A17P1 - 18

    1. If the check is satisfactory, continue with next step.
    2. If the check is not satisfactory, repair defective wiring.

  5. Confirm presence of the Ground at the left VHF (A7).

    Measurement at Expected Result Result
    Conn. A7P1 - 59 Aircraft Ground (PWR GND)
    Conn. A7P1 - 65 Aircraft Ground (PWR GND)
    Conn. A7P1 - 60 Aircraft Ground (Chassis GND)

    1. If the check is satisfactory, continue with next step.
    2. If the check is not satisfactory, repair defective wire.

  6. Confirm presence of the 28 VDC at the left VHF (A7).

    Measurement at Expected Result Result
    Conn. A7P1 - 58 28 VDC
    Conn. A7P1 - 64 28 VDC

    1. If the check is satisfactory, do close out.
    2. If the check is not satisfactory, continue with next step.

  7. Do wiring check between left VHF (A7) and left Circuit Breaker Panel (CBP1) for the following wires:

    From To Result
    Conn. A7P1 - 58 CBP1J2 - K
    Conn. A7P1 - 64 CBP1J2 - K

    1. If the check is satisfactory, continue with next step.
    2. If the check is not satisfactory, repair defective wiring.

  8. Replace COM 1 Circuit Breaker (CB1-B2). Is the fault message still present?

    1. If YES, continue with next step.
    2. If NO, do close out.

  9. Replace left Circuit Breaker Panel (CBP1).
  10. Do close out.

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