Cummins/Onan — Testing DC Armature Windings
Testing & diagnosis · Armature DC windings
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan MCCK
Procedure
- Open circuit test: touch one prod to a commutator bar and the other to successive bars around the commutator.
- If light does not glow and buzzer does not buzz, there is an open DC winding; replace the armature.
- Short circuit test: place armature in a growler and hold a steel strip about 1/2 inch (13 mm) above the laminations.
- If the strip is magnetically attracted at any point, a short circuit exists; replace the armature.
- Ground test: place one prod on the armature shaft and the other on a commutator bar.
- If tester lights or buzzer sounds, a grounded circuit is indicated; replace the armature.
- Test between AC and DC circuits with one prod on the commutator and one on the slip rings.
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 MCCK →
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.