Generac — Testing the Stepper Motor
Testing & diagnosis
From a Generac service manual covering: GN-190, GN-220, NP-30G, NP-40G. Check it applies to your exact model before use.
Applies to: Generac NP-30G, Generac GN-190 / GN-220 engine, Generac GN-220 engine
Procedure
- Unplug the Stepper Motor connector from its receptacle on the CCG circuit board.
- Set a VOM to its Rx1 scale and zero the meter.
- Connect one probe to the connector pin for the RED wire and the other probe to the ORANGE, YELLOW, BROWN and BLACK pins in turn; each should read 19-21 ohms.
- To test for a shorted condition, set the VOM to Rx10,000 or Rx1K and zero the meter.
- Connect one probe to the RED wire connector pin and the other to the Stepper Motor case; meter should read infinity.
- Replace the Stepper Motor if it fails any part of the test.
Tools required
- VOM (volt-ohm-milliammeter) Amazon
Tool links are Amazon searches (affiliate links); manufacturer special tools may only be available from a dealer.
Specs & values
- Each winding 19-21 SinoCMP $119.00 ohms
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.