Cummins/Onan — Generator/PCC Control Isolation Procedure
Testing & diagnosis · Generator / PowerCommand control
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan DFE
Before you start
- This test involves unregulated excitation of the generator. To prevent damage due to overcurrent, make sure all loads are disconnected and all faults cleared.
- HAZARDOUS VOLTAGE. Touching uninsulated parts inside the control housing and power output boxes can result in severe personal injury or death.
Procedure
- Throw line circuit breaker OFF and shut down the set.
- Open control box, remove plug 10 from connector 10 of voltage regulator output module (A37).
- Prepare to measure output voltage across generator terminals while running.
- Bring two 12V battery jumpers to X (Field +) and XX (Field -) pins of plug 10.
- Check polarity again; polarity must be correct or test is inconclusive.
- Start set and connect jumper from battery negative (-) to XX lead.
- If rated or higher voltage and balanced phases, generator is probably okay; troubleshoot PCC.
- If voltages unbalanced, troubleshoot main stator first; if uniformly low, troubleshoot exciter and field circuits.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- X = Red wire of connector 10-6
- XX = Brown wire of connector 10-3
- Normal excitation voltage approximately 10 VDC no-load to 40 VDC full-load
Full service-parts list: Cummins/Onan DFE →
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.