Cummins/Onan — Adjusting AC Output Voltage (Non-PMG) Using Digital Display
Adjustments · Alternator / genset controller
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan MDDC
Procedure
- Start genset, let voltage and frequency stabilize 5 to 10 seconds; disconnect all loads.
- Rapidly press START 6 times during the first minute after startup to enter voltage adjust mode.
- Press and quickly release START to raise voltage about 0.6 volts per press.
- Press and hold START about 1 second to lower voltage about 0.6 volts per press.
- Wait about 20 seconds for display to return to Running, then press STOP to save.
- Restart the genset and check voltage.
Tools required
- Separate voltmeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Voltage changes approximately 0.6 volts each press and release
Full service-parts list: Cummins/Onan MDDC →
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.