Facts About Generators
GeneratorsDirectoryCompareRepairEnginesControllersPartsManufacturersGuides
Search models or part #
Home›Repair guides›TESTING ROTATING RECTIFIERS

Cummins/Onan — TESTING ROTATING RECTIFIERS

For these Cummins/Onan models: MDL3, MDL4, MDL6.

Applies to: Cummins Onan Mdl3, Cummins Onan Mdl4, Cummins Onan Mdl6

Procedure

  1. Disconnect all leads from assembly to be tested.
  2. Connect one test lead to F1+ stud and connect other lead to CRI, CR2, and CR3 in turn; record resistance value of each rectifier.
  3. Connect one lead to F2- stud and connect other lead to CR4, CR5, and CR6 in turn; record resist- ance valve of each rectifier.
  4. Reverse ohmmeter leads from steps 2 and 3 and record resistance value of each rectifier F1+ to CRI, CR2, and CR3 and F2- to CR4, CR5, and CR6.
  5. All the resistance readings should be high in one test and low in the other test. If any reading is high or low in both tests, rectifier assembly is defective.
  6. Replace defective rectifier assembly with new identical part. Use 23 to 26 inch Ibs (2.6 to 2.9 Nom) torque when replacing nuts of F1+ and F2-, CR1, CR2, CR3, CR4, CR5, and CR6. CR'? OHMMETER.

Specs & torque values

  • 3
  • 6
  • 26

Source: manual:934-0500 Onan MDL3 MDL4 MDL6 Marine Genset Service manual (08-1991).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.