Cummins/Onan — Winding Insulation Resistance Test
Testing & diagnosis · generator
From a Cummins/Onan service manual — check it applies to your exact model before use.
Applies to: Cummins/Onan MDKB, Kubota D1105 engine, Kubota V1305 engine, Kubota V1505 engine, Kubota V1903B engine, Kubota V2203B engine, Kubota V2803B engine, Kubota V3300-E2B engine
Procedure
- Apply 500 VAC megger between winding and ground for 10 minutes
- Record resistance at 1 minute and again at 10 minutes
- New generator with dry windings should read at least 5 megohms, polarization index at least 2
- In-service set should not read less than 1 megohm, polarization index not less than 2
- Dry windings and repeat test if low readings obtained
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
- 5 megohms minimum (new, dry)
- 1 megohm minimum (in service)
- polarization index >= 2
Full service-parts list: Cummins/Onan MDKB →, Kubota D1105 engine →, Kubota V1305 engine →, Kubota V1903B engine →, Kubota V3300-E2B engine →
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.