Cummins/Onan — Field Flashing
Repair & overhaul · Voltage regulator VR21 / generator field
From a Cummins/Onan service manual — check it applies to your exact model before use.
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Before you start
- The voltage regulator could be damaged if the flashing circuit is connected for more than 5 seconds.
- HAZARDOUS VOLTAGE! Stand on a dry wooden platform or rubber insulating mat, make sure clothing and shoes are dry, remove jewelry and use tools with insulated handles.
Procedure
- Assemble a 12 volt battery, 10 ohm resistor, 18 volt voltage suppressor and 12 amp 300 volt diode.
- While the set runs at nominal frequency, momentarily connect the positive (+) side to voltage regulator terminal VR21-F1 (X).
- Connect the negative (-) side to voltage regulator terminal VR21-F2 (XX).
- Check output voltage, shut down the set and restart it.
Tools required
- 12 volt battery Amazon
- 10 ohm resistor Amazon
- 18 volt voltage suppressor Amazon
- 12 A, 300 V diode Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
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.