02/25/21
Message Overview:
Message Description:
The Left Bus Tie Contactor (LBTC) has failed.
Possible Causes:
- Left Bus Tie Contactor (LBTC) (K79)
- Left DC Power-Center Primary-Logic (LLOG) (PCB3)
- Right DC Power-Center Primary-Logic (RLOG) (PCB4)
- Left Battery-Diode Printed-Circuit-Board (PCB21)
- Left DC Power Center (LDCPC) (A35)
- Right DC Power Center (RDCPC) (A36)
- Associated Wiring
Troubleshooting Tips:
Advisory Wire/Service Bulletin:
- AW300-24-0024 - Electrical System - Troubleshooting Tips
- AW300-24-0137 - Y06 Electrical System Upgrade
- AW300-24-0162 - Service Bulletin 100-24-20 - DC Power Center (DCPC) System - Inspection and Replacement of Internal Fuses in the L/H and R/H DC Power Center (DCPC)
Forum Articles/Infoservice/Newsletter: None
Quick Links:
| Removal of the Power Center (DCPC) | AMM 24-61-01-000-801 |
| Installation of the Power Center (DCPC) | AMM 24-61-01-400-801 |
| Removal of the Bus Tie Contactor | AMM 24-61-29-000-801 |
| Installation of the Bus Tie Contactor | AMM 24-61-29-400-801 |
| Removal of the DC Power-Center Primary-Logic | AMM 24-61-73-000-801 |
| Installation of the DC Power-Center Primary-Logic | AMM 24-61-73-400-801 |
| Removal of the DCPC Battery-Diode Printed-Circuit Board | AMM 24-61-82-000-801 |
| Installation of the DCPC Battery-Diode Printed-Circuit Board | AMM 24-61-82-400-801 |
| Standard Practices - Replace Wiring | SPM 20-12-00-02 |
| Standard Practices - Wire Repair | SPM 20-12-10-02 |
Troubleshooting Recommendations:
- Disconnect the Left Bus Tie Contactor (K79) connector and the Left DCPC Battery-Diode PCB (PCB21) located in the Left DC Power Center (A35). Do visual inspection of the connectors and associated wiring for any loose pins and/or damaged wire.
- If inspection is satisfying, continue with next step.
- If inspection is not satisfying, go to step 7.
- Verify Left Bus Tie Contactor (K79) coils by measuring the resistances at the contactor connector (J-side) as per the following table:
Coils Expected Values Results Pin 1 and Pin 2 (Pick-up) between 4.5Ω and 6.5Ω Pin 2 and Pin 3 (Hold) between 260Ω and 280Ω - If the verification is satisfying, continue with next step.
- If the verification is not satisfying, replace the defective Bus Tie Contactor.
NOTE: It is important to not skip this verification before proceeding with the swap at step 3. A short of one of the 2 coils will result with a blowing of a fuse on the Left DC Power-Center Primary-Logic (PCB3) and on the Right DC Power-Center Primary-Logic (PCB4).
- Swap the Left Bus Tie Contactor (K79) with the Right Bus Tie Contactor (K80). Is the fault message still present?
- If YES, continue with next step.
- If NO, replace the defective Bus Tie Contactor.
- Swap the Left DC Power-Center Primary-Logic (PCB3) with the Right DC Power-Center Primary-Logic (PCB4). Is the fault message still present?
- If YES, continue with next step.
- If NO, replace the defective DC Power-Center Primary-Logic.
- Swap the Left DCPC Battery-Diode PCB (PCB21) with the Right DCPC Battery-Diode PCB (PCB20). Is the fault message still present?
- If YES, continue with next step.
- If NO, replace the defective DCPC Battery-Diode PCB.
- Do wiring check between the Left D Power Center (A35) and Right DC Power Center (A36) as per the following table. Repair wiring as required. Is the fault message still present?
From To Results LDCPC Conn. A35P2 pin z RDCPC Conn. A36P2 pin z LDCPC Conn. A35P2 pin y RDCPC Conn. A36P2 pin y LDCPC Conn. A35P2 pin B RDCPC Conn. A36P2 pin B - If YES, continue with next step.
- If NO, do close out.
- Replace Left DC Power Center (A35). Is the fault message still present?
- If YES, continue with next step.
- If NO, do close out.
- Replace Right DC Power Center (A36).
- Do close out.
