Kohler — Governor System Operation Test Procedure

Testing & diagnosis · Governor system / magnetic pickup

From a Kohler service manual covering: 12RES, 8.5/12 RES, 8.5RES. Check it applies to your exact model before use.

Applies to: Kohler 12RES, Kohler 8.5RES, Kohler CH20 engine, Kohler CH 740 engine

Procedure

1. Verify carburetor throttle linkage is connected to the stepper motor.
2. Look for broken or loose wiring or plug connections if stepper motor moves erratically.
3. Check stepper motor operation at startup; note throttle positions.
4. If throttle moves fully open then steps to and stays fully closed, check the magnetic pickup.
5. Connect a voltmeter to the magnetic pickup leads; check for 1.75 volts AC minimum during cranking.
6. If below 1.75 VAC, verify magnetic pickup air gap is 0.5 mm (0.020 in.); adjust as needed.
7. After adjusting gap, recheck voltage; replace magnetic pickup if still below 1.75 VAC.
8. Disconnect magnetic pickup leads and open circuit breaker to test controller governing function.
9. Move throttle shaft/stepper motor fully counterclockwise (closed throttle).
10. Start the generator set; stepper motor should step clockwise to wide open throttle and remain there.
11. Place master switch in STOP; check stepper motor connections (leads 1A, 1B, 2A, 2B to P1-4, P1-5, P1-6, P1-7).
12. Check stepper motor coil resistance across pins 2 and 3 and across pins 1 and 4.

Full service-parts list: Kohler 12RES →, Kohler 8.5RES →

Source: Kohler 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.

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