Cummins/Onan — Circuit Breaker Resistance Check
Testing & diagnosis · AC load circuit breaker
From a Cummins/Onan service manual covering: 4BT3.9, 4BT3.9-GC1, 4BT3.9-GC2, 6BT5.9, 6BT5.9-GC1, 6BT5.9-GC2, 6CT8.3, 6CT8.3-GS/GC1, 6CTA8.3, 6CTA8.3-GS/GC1, 6CTA8.3-GS/GC2. Check it applies to your exact model before use.
Applies to: Cummins/Onan 4BT3.9, Cummins/Onan 6BT5.9, Cummins/Onan 6CTA8.3, Cummins/Onan 4BT3.9 engine, Cummins/Onan 6BT5.9 engine, Cummins/Onan 6CT8.3 engine, Cummins/Onan 6CTA8.3 engine
Before you start
- Place Run/Stop/Remote switch in Stop position and disconnect battery negative (-) cable.
Procedure
- Disconnect the line and load wires from the circuit breaker.
- Move breaker handle to On position and check resistance across each pole (line to load).
- Resistance should be very low (near zero) and relatively equal across all poles.
Tools required
- Ohmmeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Resistance near zero and equal across all poles
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.