Cummins/Onan — Testing Exciter Rotor (Armature)
Testing & diagnosis · Exciter rotor/armature
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan DFM
Procedure
- Testing for grounds: remove diodes CR1 through CR6 from diode heat sink assemblies
- Using ohmmeter (R x 100 scale) measure insulation resistance between any lead and the laminations (exclude diodes)
- Testing winding resistance: use a Wheatstone or Kelvin bridge, measure between lead pairs T1-T2, T2-T3 and T1-T3
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Resistance should be 0.496-0.607 ohms at 20°C (68°F)
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.