Cummins/Onan 3100 series — Testing the Generator Stator and Rotor Windings
Testing & diagnosis · Main stator, main rotor, exciter stator, exciter rotor
For the Cummins/Onan 3100 series, from the Cummins/Onan service manual.
Applies to: Cummins/Onan DGBB, Cummins/Onan DGBC, Cummins/Onan DGCA, Cummins/Onan DGCB, Cummins/Onan DGCC, Cummins/Onan DGDA, Cummins/Onan DGDB, Cummins/Onan DGDK, Cummins/Onan DGEA, Cummins/Onan DGFA, Cummins/Onan DGFC
Before you start
- Disconnect the starting battery cables (negative [-] first) to make sure the engine will not start while performing these tests.
Procedure
- Disconnect battery cables (negative first) so the engine will not start.
- Measure winding resistance with a Wheatstone bridge or digital ohmmeter and compare to Table 6-1.
- Measure winding insulation resistance between leads and laminations; replace if less than 1 megohm.
- For the main stator, measure across each pair of stator leads (U1-U2, U5-U6, V1-V2, V5-V6, W1-W2, W5-W6).
Tools required
- Wheatstone bridge or digital ohmmeter (0.001 ohm precision) Amazon
- Megger or insulation resistance meter Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Insulation resistance must be at least 1 megohm (1,000,000 ohms)
- See Table 6-1 generator winding resistances
Full service-parts list: Cummins/Onan DGBB →, Cummins/Onan DGBC →, Cummins/Onan DGCA →, Cummins/Onan DGCB →, Cummins/Onan DGCC →, Cummins/Onan DGDA →, Cummins/Onan DGDB →, Cummins/Onan DGEA →, Cummins/Onan DGFA →, Cummins/Onan DGFC →
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.