Cummins/Onan — Testing Exciter Stator
Testing & diagnosis
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan MDKC, Cummins/Onan MDKD, Cummins/Onan RGA-OP'
Procedure
- Disconnect F1+ and F2- exciter field leads from terminal block in generator end bell.
- Measure resistance between field leads with a Wheatstone bridge or digital ohmmeter.
- Resistance should be 11.16 to 13.64 ohms at 77°F (25°C).
- Apply 500 VDC or more between either field lead and the exciter stator lamination.
- Insulation reading should be 1,000,000 ohms or greater.
- A shorted stator must be replaced.
Tools required
- Wheatstone bridge or digital ohmmeter Amazon
- Megger or insulation resistance meter (500 VDC or more) Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Field lead resistance 11.16 to 13.64 ohms at 77°F (25°C).
- Ground reading 1,000,000 ohms or greater.
Full service-parts list: Cummins/Onan MDKC →, Cummins/Onan MDKD →, Cummins/Onan RGA-OP' →
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.