Cummins/Onan QST30 — Insulation Resistance Testing
Testing & diagnosis · 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
- Disconnect negative battery cable first.
Procedure
- Disconnect plug J10 from voltage regulator output stage module.
- Disconnect AC control input leads marked 5,6,7,8 from alternator output terminals.
- If RTD option installed, ground all six RTD temperature leads (18 leads total).
- Perform Insulation Resistance Test procedure for desired windings.
Tools required
- 500 VAC megger Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- P7 main stator minimum 10.0 − 1.0 MΩ
- HC6 main stator minimum 5.0 − 1.0 MΩ
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.