02/23/21
Message Overview:
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 |
| Wiring - Maintenance Practices - ALL | SPM 20-12-00-02 |
| Wire Repair - Maintenance Practices - ALL | SPM 20-12-10-02 |
| Electrical Connectors - Maintenance Practice - ALL | SPM 20-20-00-02 |
Troubleshooting Recommendations:
- Reset COM 1 Circuit Breaker CB1-B2. Is the fault message still present?
- If YES, continue with next step.
- If NO, do close out.
- Swap left VHF (A7) with right VHF (A8). Is the fault message still present?
- If YES, continue with next step.
- If NO, replace defective VHF.
- Swap left RIU (A17) with right RIU (A18). Is the fault message still present?
- If YES, continue with next step.
- If NO, replace defective RIU.
- 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 - If the check is satisfactory, continue with next step.
- If the check is not satisfactory, repair defective wire.
- 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) - If the check is satisfactory, continue with next step.
- If the check is not satisfactory, repair defective wire.
- 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 - If the check is satisfactory, do close out.
- If the check is not satisfactory, continue with next step.
- 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 - If the check is satisfactory, continue with next step.
- If the check is not satisfactory, repair defective wire.
- Replace COM 1 Circuit Breaker (CB1-B2). Is the fault message still present?
- If YES, continue with next step.
- If NO, do close out.
- Replace left Circuit Breaker Panel (CBP1).
- Do close out.