Cummins/Onan QST30 — Drying the Windings
Repair & overhaul · Alternator windings
For the Cummins/Onan QST30, from the Cummins/Onan service manual.
Applies to: Cummins/Onan DFHA, Cummins/Onan DFHB, Cummins/Onan DFHC, Cummins/Onan DFHD, Cummins/Onan QST30, Cummins/Onan QST30 engine
Before you start
- Voltage must begin at zero volts and be gradually increased.
- Monitor current to prevent exceeding alternator rating.
Procedure
- Bolt alternator three phase output terminals together.
- Remove accessory box cover and remove plug P10 from J10 of voltage regulator output module.
- Connect positive lead to P10-6 red wire (X), negative to P10-3 brown wire (XX).
- Attach clamp-on ammeter to alternator leads. Adjust 12 VDC source for zero voltage.
- Start set and very slowly increase excitation voltage to highest current without exceeding rating.
- Run generator set approximately one hour, then repeat insulation resistance tests.
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 DFHA →, Cummins/Onan DFHB →, Cummins/Onan DFHC →, Cummins/Onan DFHD →, Cummins/Onan QST30 →
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.