Cummins/Onan — Voltage Adjustment (VR21)
Adjustments · Voltage regulator VR21
From a Cummins/Onan service manual covering: 300.0 DFT, 350.0 DFU, 350.0 WF, 400.0 DFV, 400.0 WK, 450.0 DFW, 500.0 DFY, 600.0 DWV. Check it applies to your exact model before use.
Applies to: Cummins/Onan YB series
Procedure
- Center the voltage adjust knob so pointer is vertical.
- Open meter panel doors. Start unit.
- Using a screwdriver, turn R18 potentiometer on printed circuit board VR21.
- Observe voltmeter on meter panel while adjusting. Set voltage with no load connected. Example: for 120/240 volt connection, set at approximately 246 volts.
- If voltage is unstable or tends to hunt, turn R26 potentiometer to increase voltage dampening.
Tools required
- screwdriver Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Approximately 246 volts for 120/240V connection
Full service-parts list: Cummins/Onan YB series →
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.