Cummins/Onan — Control Board A1 Testing
Testing & diagnosis
From a Cummins/Onan service manual — check it applies to your exact model before use.
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Procedure
- Disconnect negative battery cable.
- Remove control box cover; separate it from control board A1.
- Check electrical continuity across each P1/J1 and P3/J3 connector.
- Reconnect battery; try to start and run set.
- Measure voltage at connector P1-2 while pressing start switch (ground at P1-8).
- Replace control board A1 if voltmeter indicates zero volts.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- At least 9 volts indicates problem is not the control board
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.