Cummins/Onan — Testing Rotating Rectifier Assembly

For these Cummins/Onan models: MDTNDTA, PROTEC series, SK, Standard YD Generator and Regulator, YD PTO.

Applies to: Cummins Onan Mdtndta, Cummins Onan Protec Series, Cummins Onan Standard Yd Generator And Regulator, Cummins Onan Yd Pto

Procedure

1. Disconnect all leads from assembly to be tested.
2. Connect one test lead to F1+ stud and connect other lead to CR1, CR2, and CR3 in turn; record resistance value of each rectifier.
3. Connect one lead to F2- stud and connect other lead to CR3, CR4 and CR5 in turn; record resistance value of each rectifier.
4. Reverse ohmmeter leads from step 2 and record resistance value of each rectifier F1+ to CR1, CR2, and CR3 and F2- to CR4, CR5, and CR6.
5. Verify all three resistance readings should be high in one test and low in the other test.
6. If any reading is high or low in both tests, rectifier assembly is defective.
7. Replace defective rectifier assembly with new identical part.
8. Use 24 Ibs-in. (27 N·m) torque when tightening nuts on F1+ and F2-.

Source: manual:900-0184 Onan YD Generators & Controls Service manual (11-1983)L.pdf. Figures and steps are as documented; always cross-check against the official manual and any later revisions for your exact serial number before servicing.