Cummins/Onan — Line Circuit Breaker Troubleshooting
Testing & diagnosis
From a Cummins/Onan service manual covering: C13 N6H, C13N6H, C17 N6H, C17N6H, C20 N6, C20N6H, RS13A. Check it applies to your exact model before use.
Applies to: Cummins/Onan C13 N6H, Cummins/Onan C17 N6H, Cummins/Onan C20 N6, Cummins/Onan RS13A
Before you start
- Automated Machinery: accidental or remote starting can cause severe personal injury or death.
Procedure
- Shut down and disable the generator set; disconnect the negative (–) battery cable and reconnect it last when done.
- Disconnect the leads going into and out of the circuit breaker (two leads from the alternator at the top L1 and L2, and two from customer wiring at the bottom L1 and L2).
- Check continuity: with the breaker on, very low resistance between the L1 lugs and between the L2 lugs.
- With the breaker off, the continuity check between L1 and L2 pairs should show open.
- Replace the breaker if either of the continuity tests fails.
Tools required
- Ohmmeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Full service-parts list: Cummins/Onan C20 N6 →
Source: Cummins/Onan service manual. Steps and values are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.