02/24/21
Message Overview:
Message Description:
Third VHF is not transmitting ARINC data to L RIU.
Possible Causes:
- Third VHF Communication Unit (VHF 3) (A10)
- Left Radio Interface Unit (RIU 1) (A17)
- VHF 3 Circuit Breaker (CB3-E2)
- Left Secondary Power Center (LSPC) (A37)
- 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 |
| Removal of the Secondary Power Center (SPC) | AMM 24-62-01-000-801 |
| Installation of the Secondary Power Center (SPC) | AMM 24-62-01-400-801 |
| Replacement of DC Circuit Breakers | AMM 24-65-00-960-801 |
| 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 VHF 3 Circuit Breaker CB3-E2. Is the fault message still present?
- If YES, continue with next step.
- If NO, do close out.
- 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 Third VHF (A10) and left RUI (A17) for the following wires:
From To Result Conn. A10P1 - 17 Conn. A17P1 - 23 Conn. A10P1 - 18 Conn. A17P1 - 24 - If the check is satisfactory, continue with next step.
- If the check is not satisfactory, repair defective wiring.
- Confirm presence of the Ground at the Third VHF (A10).
Measurement at Expected Result Result Conn. A10P1 - 59 Aircraft Ground (PWR GND) Conn. A10P1 - 65 Aircraft Ground (PWR GND) Conn. A10P1 - 60 Aircraft Ground (Chassis GND) - If the check is satisfactory, continue with next step.
- If the check is not satisfactory, repair defective wiring.
- Confirm presence of the 28 VDC at the Third VHF (A10).
Measurement at Expected Result Result Conn. A10P1 - 58 28 VDC Conn. A10P1 - 64 28 VDC - If the check is satisfactory, continue with step 8.
- If the check is not satisfactory, continue with next step.
- Do wiring check between Third VHF (A10) and left Secondary Power Center (A37) for the following wires:
From To Result Conn. A10P1 - 58 A37P4 - a Conn. A10P1 - 64 A37P4 - a - If the check is satisfactory, continue with next step.
- If the check is not satisfactory, repair defective wiring.
- Replace VHF 3 Circuit Breaker (CB3-E2). Is the fault message still present?
- If YES, replace defective left Secondary Power Center (A37).
- If NO, do close out.
- Replace third VHF (A10). Is the fault message still present?
NOTE: Depending on the parts installed, swap test is possible to confirm failure. Verify interchangeability in AIPC 23-11-01 before proceeding. - Do close out.