Cummins/Onan 3.6MKY / 4MKY — Rotor Test (Ground, Open, Short)
Testing & diagnosis
For the Cummins/Onan 3.6MKY / 4MKY, from the Cummins/Onan service manual.
Applies to: Cummins/Onan 3.6MKY, Cummins/Onan 4MKY
Procedure
- Ground Test: touch one prod to the rotor shaft and the other to a slip ring; infinity should be measured.
- A reading less than one megohm indicates a grounded rotor - replace.
- Open Test: place prods on the slip rings; continuity of 19-27 ohms should be indicated.
- Short Test: set ohmmeter to lowest scale; less than 17 ohms at 77° F (25° C) indicates shorted windings - replace.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 19-27 ohms across slip rings
- less than 17 ohms = shorted
- less than one megohm = grounded
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.