Fault Message:

ACPC AC 3 FEEDER CONTACTOR-K21 FAIL

Fault Code:

2451356ACP

Associated CAS:

ELEC SYS FAIL
Caution

Secondary Logic Card 3 detects a discrepancy between the coil drive status and auxiliary contact status of the K21 Contactor.

• AC Power Center (ACPC) (A54)
• AC Power Center (ACPC) Contactor (K21)
• AC Power Center (ACPC) TB402
• AC Power Center (ACPC) TB302
• Secondary Logic Card (SLC) 3
• Electronic Module 2 (EM2)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter: None

If AC BUS 3 FEEDER (K21) is tripped and is not resettable:

1. Check K21 output (A2/B2/C2) and make sure all the three phases are not shorted to ground.
2. Do a resistance check between current transformer IS5A and common, IS5B and common and IS5C and common. Make sure that the resistance values on each phase is approximately the same.

1. Swap SLC 3 with SLC 2.

   1. If system checks are good, replace SLC 3 and do close out.
   2. If fault remains, continue with next step.

2. Perform a voltage check as follows:

   From	To	Result
   K21-X1	Ground
   K21 -Y1	Ground

   1. If no voltage and there are no CAIMS messages related to EM2 fuses (F1, F2, F3 and F4), continue with next step.
   2. If no voltage and there is CAIMS messages related to EM 2 Fuses (F1, F2, F3 and F4), troubleshoot these messages first and continue with next step.
   3. If there is 28 VDC, go to step 4.

3. Verify voltage check on TB402-1 and TB302-1.

   1. If system checks are good, continue with next step.
   2. If fault remains, repair defective wiring as required and do close out.

4. Remove SLC 3 and disconnect K21-X1, K21-X2, K21-Y1, K21-Y2, K21-Y11 and K21-12.
5. Perform a continuity check as follows:

   From	To	Result
   K21-11 (lug)	Ground

   1. If there is continuity, repair defective wiring as required and do close out.
   2. If there is no continuity, continue with next step.

6. Perform a continuity check between the connections as follows:

   From	To	Result
   K21-Y2 (lug)	Ground
   K21-X2 (lug)	Ground
   K21-12 (lug)	Ground

   1. If there is continuity, go to step 9.
   2. If there is no continuity, continue with next step.

7. Perform a continuity check between the connections as follows:

   From	To	Result
   K21-Y2 (lug)	P310A-10
   K21-X2 (lug)	P310A-11
   K21-12 (lug)	P311C-19

   1. If there is continuity, continue with next step.
   2. If there is no continuity, go to step 9.

8. Replace contactor K21.

   1. If system checks are good, do close out.
   2. If fault remains, continue with next step.

9. Replace ACPC.
10. Do close out.