05/06/21
Message Overview:
Message Description:
The Right Essential Bus Contactor (RESSC) has failed.
Possible Causes:
- Right Essential Bus Contactor (RESSC) (K78)
- Right DC Power-Center Primary-Logic (RLOG) (PCB4)
- Right DC Power Center (RDCPC) (A36)
- Associated Wiring
Troubleshooting Tips:
Advisory Wire/Service Bulletin:
- 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 Essential Contactor | AMM 24-61-25-000-801 |
| Installation of the Essential Contactor | AMM 24-61-25-400-801 |
| 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 |
| Standard Practices - Replace Wiring | SPM 20-12-00-02 |
| Standard Practices - Wire Repair | SPM 20-12-10-02 |
Troubleshooting Recommendations:
- Disconnect the Right Essential Bus Contactor (K78) connector located in the Right DC Power Center (A36). Do visual inspection of the connector 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 5.
- Verify Right Essential Bus Contactor (K78) 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 Essential Bus Contactor.
NOTE: It is important to not skip this verification before proceeding with the interchange 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).
- Interchange the Right Essential Bus Contactor (K78) with the Left Essential Bus Contactor (K77). Is the fault message still present?
- If YES, continue with next step.
- If NO, replace the defective Essential Bus Contactor.
- Interchange the Right DC Power-Center Primary-Logic (PCB4) with the Left DC Power-Center Primary-Logic (PCB3). Is the fault message still present?
- If YES, continue with next step.
- If NO, replace the defective DC Power-Center Primary-Logic.
- Replace Right DC Power Center (A36).
- Do close out.
