Cummins/Onan PCC Control 3100 Series — Generator/PCC Control Isolation Procedure
Testing & diagnosis · Generator / PCC control
For the Cummins/Onan PCC Control 3100 Series, from the Cummins/Onan service manual.
Applies to: Cummins/Onan DFAA, Cummins/Onan DFAB, Cummins/Onan DFAC, Cummins/Onan DFBF, Cummins/Onan DFCB, Cummins/Onan DFCC, Cummins/Onan DFCE, Cummins/Onan DFE
Before you start
- This test involves unregulated excitation of the generator; make sure all loads have been disconnected.
- HIGH VOLTAGE: touching uninsulated high voltage parts inside the control box can result in severe personal injury or death.
Procedure
- Throw the line circuit breaker OFF and shut down the set.
- Remove the accessory box housing cover and remove plug P10 from connector J10 of A37.
- Prepare to measure output voltage across the generator terminals while the set is running.
- Bring two jumpers from a 12 volt battery for connection to X (Field +) and XX (Field -) pins of plug P10.
- Check polarity again; polarity must be correct or the test will be inconclusive.
- Start the set and connect the jumper from the battery negative terminal to the XX lead.
- If rated output voltage or higher is obtained and all phases are balanced, generator circuitry is probably okay; refer to Section 4.
- If voltages are unbalanced, troubleshoot the main stator first; if uniformly low, troubleshoot exciter and field circuits first.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Normal excitation voltage ranges from approximately 10 VDC at no-load to approximately 40 VDC at full-load.
Full service-parts list: Cummins/Onan DFBF →, Cummins/Onan DFCC →, Cummins/Onan DFCE →, 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.