Fault Message:

GEN4 [PHASE NEUTRAL CROSSED]

Fault Code:

2424109LPS

Associated CAS:

GEN 4 FAIL
(Advisory)

Variable Frequency Generator (VFG) 4 has tripped off-line or will not come on-line.

• Ground Stud (GS153)
• Generator Control Unit (GCU) 4 (A59)
• Variable Frequency Generator (VFG) 4 (G4)
• AC Power Center (ACPC) (A54)
• Associated Wiring

Advisory Wire/Service Bulletin: None

Forum Articles/Infoservice/Newsletter:

• Forum Newsletter Volume 13 issue 16 August 2016

NOTE: The Generator ground stud connection may need to be visually inspected for signs of arcing.

A GCU patch cable (GSE REF # 24X-24-02) can be used to swap GCU 1, GCU 2, GCU 3, GCU 4 and the APU GCU into a different position (for troubleshooting only). You can monitor the GCU faults in CAIMS via the active fault page.

1. At VFG 4, perform a check of the output connections at the terminal block. Are the connections as shown in the table below?

   Connection	Color
   T1	White
   T2	Blue
   T3	Orange
   G	Green

   1. If NO, reconnect or repair as required and do close out.
   2. If YES, continue with next step.

2. At the ACPC, perform a check of the VFG input terminals at VFG 4 LCTA 4. Are the connections as shown in the table below?

   Connection	Color
   T1	White
   T2	Blue
   T3	Orange

   1. If NO, reconnect or repair as required and do close out.
   2. If YES, continue with next step.

3. Perform a bonding test of ground stud GS153 as follow:

   From	To	Expected Result	Result
   GS153	Ground	<0.010 ohms

   1. If the resistance value is higher than 0.010 ohms, repair ground stud and do close out.
   2. If the resistance value is good, continue with next step.

4. Swap GCU 4 with GCU 3 (physically or using the GCU patch cable). Is the fault still present?

   1. If NO, replace GCU 4 and do close out.
   2. If YES, continue with next step.

5. Disconnect GCU 4 connector A59P1 and ACPC connector A54P2. Perform a continuity check as follows:

   From	To	Result
   A59P1-A	Ground
   A59P1-B	Ground
   A59P1-C	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 as follows:

   From	To	Result
   A59P1-A	A54P2-A
   A59P1-B	A54P2-B
   A59P1-C	A54P2-C

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

7. Swap VFG 4 with VFG 3. Is the fault still present?

   1. If NO, replace VFG 4 and do close out.
   2. If YES, continue with next step.

8. Replace ACPC.
9. Do close out.