Cummins/Onan A15 — Servicing the PMG
Testing & diagnosis · PMG exciter
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
Before you start
- Touching uninsulated high voltage parts can result in severe personal injury or death.
Procedure
- Disconnect leads P2, P3, P4 from voltage regulator.
- Start engine and let speed stabilize.
- Measure voltage across lead pairs P2-P3, P3-P4, P4-P2; should be at least 150 VAC (50Hz) or 180 VAC (60Hz).
- Stop set and measure resistance across same lead pairs; each winding approximately 4.4 ohms.
- Torque PMG rotor center bolt to 40 ft-lbs (54 Nm) when reassembling; stator leads must be at 12 o'clock.
Tools required
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 150/180 VAC minimum
- 4.4 ohms per winding
- rotor center bolt 40 ft-lbs (54 Nm)
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.