Cummins/Onan — Rectifier Checkout
Testing & diagnosis
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
Before you start
- Note carefully the direction of mounting of any rectifier removed. It must be remounted in its original direction.
Procedure
- Disconnect one lead from, or remove, each rectifier for its individual test.
- Connect ohmmeter across rectifier contacts and observe meter reading.
- Reverse connections and compare new reading with first reading.
- If one reading is considerably higher, rectifier is satisfactory. If both readings are low or open, replace with new identical part.
Tools required
- ohmmeter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
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.