Generac NP-30G / NP-40G — Testing the Stator with a VOM
Testing & diagnosis · AC Generator Stator
For the Generac NP-30G / NP-40G, from the Generac service manual.
Applies to: Generac NP-30G, Generac GN-190 / GN-220 engine, Generac GN-190 or GN-220 (see NOTE 2) engine, Generac GN-220 engine
Before you start
- All stator leads must be disconnected and isolated before testing.
Procedure
- Disconnect stator power phase leads AC1, AC2, SL1, SL2 at the Genistor and lead 11 at the main circuit breaker.
- Isolate all leads and ensure none touch the frame.
- Set VOM to Rx1 scale and zero the meter.
- Connect one test lead to lead 11; measure resistance to AC1, AC2, SL1 and SL2 individually.
- To test short-to-ground, set VOM to Rx10,000 or Rx1K and measure each lead to clean frame ground (should read infinity).
- Test for shorts between windings by measuring between pairs (PS1-AC1, AC1-77, AC1-TIM1, PS1-TIM1, PS1-77, TIM1-77).
Tools required
- Volt-Ohm-Milliammeter (VOM) Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Power phase windings nominal 0.30 to 0.42 ohm
- Power supply winding 0.35-0.44 ohm
- Timing winding 0.35-0.44 ohm
Full service-parts list: Generac NP-30G →
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.