Cummins/Onan DL3 — Testing Rotating Rectifiers
Testing & diagnosis · Rotating rectifier bridge assembly
For the Cummins/Onan DL3, from the Cummins/Onan service manual.
Applies to: Cummins/Onan L Series Diesel engine
Before you start
- Contact with rotating parts can cause severe personal injury or death; keep hands and clothing away.
- Ignition of explosive battery gases can cause severe personal injury; no flame, spark, cigarette or ignition source near battery.
Procedure
- Disconnect all leads from assembly to be tested.
- Connect one test lead to F1+ stud and the other to CR1, CR2 and CR3 in turn; record resistance of each rectifier.
- Connect one lead to F2- stud and the other to CR4, CR5 and CR6 in turn; record resistance of each rectifier.
- Reverse ohmmeter leads from steps 2 and 3 and record resistance of each rectifier.
- Resistance readings should be high in one test and low in the other; if high or low in both tests, assembly is defective.
- Replace defective rectifier assembly 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.
Specs & values
- Use 23 to 26 inch lbs (2.6 to 2.9 Nm) torque when replacing nuts of F1+, F2-, CR1, CR2, CR3, CR4, CR5, CR6.
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.