Cummins/Onan — Transformer Voltage Adjustment
Adjustments · Voltage regulating transformer
From a Cummins/Onan service manual — check it applies to your exact model before use.
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Procedure
- Adjust governor as specified in Governor section first.
- With unit at no load, adjust speed adjustment nut to specified frequency and voltage.
- Stop set and change transformer tap connections to increase or decrease voltage.
- Repeat voltage check until voltage is within specified range.
- Check no-load and full-load voltage and frequency.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 60 Hz, 120 V: 62 Hz, 127.5 +/- 4.5 Volts
- 50 Hz, 110/220 V: 52 Hz, 233 +/- 9 Volts
- 50 Hz, 120/240 V: 52 Hz, 255 +/- 9 Volts
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.