Cummins/Onan — Testing Reactor
Testing & diagnosis · Commutating Reactor CMR21
From a Cummins/Onan service manual covering: JC 15.0, JC15, MDJC 10.0, MDJE 75, MJC15. Check it applies to your exact model before use.
Applies to: Cummins/Onan MDJC, Cummins/Onan MDJE, Cummins/Onan MDJF
Procedure
- Resistance between 1-2 and 3-4 should be about 0.4-ohms.
- Resistance between 1-3, 2-3, 1-4, or 2-4 should be infinity.
- Resistance from any terminal to reactor frame should be infinity.
- If any condition is not met, install a new reactor.
Tools required
- ohmmeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 0.4-ohms
- infinity
Full service-parts list: Cummins/Onan MDJC →, Cummins/Onan MDJE →, Cummins/Onan MDJF →
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.