Cummins/Onan — Ignition Module Testing
Testing & diagnosis
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan NHEL
Procedure
- Remove spark plugs and fan scroll so engine can be turned by hand.
- Connect voltmeter positive to ignition coil negative terminal; negative to ground.
- Remove all leads from positive coil terminal.
- Jumper ignition module lead to battery positive terminal.
- Rotate flywheel clockwise by hand and measure resultant voltage.
- If voltage does not switch from about 1 V to about 12 V and back, module defective.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Full service-parts list: Cummins/Onan NHEL →
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.