Generac — Rotor Insulation Resistance Test
Testing & diagnosis
From a Generac service manual covering: GPS 12500, GPS 15000, GPS 17500. Check it applies to your exact model before use.
Applies to: Generac GPS 12500, Generac GPS 15000
Before you start
- Do not apply voltage longer than one second
Procedure
- Remove brush holder to completely isolate the rotor.
- Attach all leads of all stator windings to ground.
- Connect red tester lead to positive (+) slip ring nearest rotor bearing.
- Connect black tester probe to clean frame ground on rotor shaft.
- Set tester to 1500 volts; turn switch on and observe breakdown lamp.
- Do not apply voltage longer than one second.
- If breakdown lamp lights, clean and dry rotor, then repeat test.
- If lamp lights on second test, replace rotor assembly.
Tools required
- Hi-Pot tester Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- 1500 volts
- Rotor minimum insulation resistance 1.5 megohms
Source: Generac 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.