Cummins/Onan A15 — Testing the Exciter Rotor
Testing & diagnosis
For the Cummins/Onan A15, 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 DGEA, Cummins/Onan DGFA, Cummins/Onan DGFB, Cummins/Onan B and C Series diesel engine
Procedure
- Disconnect six rotor winding leads from rectifier terminal posts.
- Measure resistance across each pair of rotor windings (U-V, V-W, W-U) with Wheatstone bridge.
- Replace whole rotor shaft assembly if resistance not per Table 7-1.
- Measure insulation resistance between any rotor winding lead/terminal and rotor laminations; replace if less than 1 megohm.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
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 DGFB →
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.