Cummins/Onan — Testing the Field Windings for an Open Circuit
Testing & diagnosis
From a Cummins/Onan owner's manual covering: 4UF-3N41, 4UF-3N42, 7UF-3N41, 7UF-3N42, 7UF-3N61. Check it applies to your exact model before use.
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Procedure
- Place one test prod on one terminal end of the field windings and the other prod on the other terminal end.
- The test lamp should light; if not, an open circuit is indicated.
- Check that the open circuit is not at the terminal leads or a loose terminal.
- An open circuit within a coil requires replacement of the set of coils.
Tools required
- Test lamp set Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Source: Cummins/Onan owner's 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.