Cummins/Onan — Voltage and Voltage Stability Adjustments
Adjustments · Voltage regulator (AVR)
From a Cummins/Onan service manual — check it applies to your exact model before use.
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
- Touching uninsulated high voltage parts inside the control and power output boxes can result in severe personal injury or death.
Procedure
- Use the control panel mounted voltage trimmer, if provided, for small voltage adjustments.
- Measure generator output voltage while running without load at nominal frequency.
- If trimmer is insufficient, lock it at midpoint.
- Turn the VOLTS pot fully counterclockwise and the STABILITY pot to its midpoint.
- If the red LED lights, refer to Jumper Reconnections and UFRO Adjustments.
- Turn the VOLTS pot clockwise until rated voltage is obtained.
- If voltage becomes unstable with a large load, turn the STABILITY pot clockwise until stable.
- Check and readjust the VOLTS pot each time the STABILITY pot is readjusted.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Voltage adjustable within +/-5 percent of rated nameplate voltage via trimmer R21.
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.