Cummins/Onan — VR21 Replacement (UR Regulator)
Maintenance · Voltage regulator PC board VR21 (UR)
From a Cummins/Onan service manual covering: 15.0YD-3G, 20.0YD-3G, 20.0YD-5DG, 25.0YD-3G, 25.0YD-5DG, 30.0YD-3G, 30.0YD-5DG, 6.0-3CS1, 7.5-3CS1. Check it applies to your exact model before use.
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Before you start
- Do not install the new PC board until all other problems have been located and corrected.
Procedure
- Stop engine.
- Disconnect and if necessary label wires VR21-1 through VR21-12.
- Remove four screws at corners.
- Remove old PC board.
- Install new PC board; secure with four screws.
- Reconnect wires at proper terminals.
- Place jumper W12 at proper terminals for your voltage code.
- Perform voltage calibration and stability adjustments.
Tools required
- screwdriver 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.