Battery
Common no-start cause. Match size, terminal layout, and cold-cranking requirements.
Kohler Error Code 3 — Overspeed Fix
What it means: The Decision-Maker controller detected engine RPM exceeding 110% of the generator’s rated speed. This triggers an immediate shutdown — the controller kills the fuel solenoid and closes the throttle.
At 1800 RPM generators, the threshold is ~1980 RPM. At 3600 RPM residential units, ~3960 RPM. The overspeed event is usually caused by something the governor can no longer control.
Common Causes
| Cause | Frequency | Fix Difficulty |
|---|---|---|
| Actuator linkage binding or corroded | High | Easy |
| Demand regulator diaphragm failed (gas/LP) | Medium | Moderate |
| Governor spring broken or disconnected | Medium | Moderate |
| Stepper motor failed | Low | Moderate |
| Controller governor output lost | Low | Hard |
Step-by-Step Fix
1. Check the Governor Actuator Linkage
The most common cause. The throttle actuator on Kohler generators moves the throttle plate to maintain steady RPM. If the linkage arm is corroded, binding, or has debris buildup, the actuator can’t close the throttle fast enough when RPM rises. Disconnect the linkage and manually move the throttle plate through its full range. Clean and lubricate if binding. On gas units, look for soot or gum buildup from fuel residue.
2. Test the Demand Regulator (Gas/LP Models)
On natural gas and LP generators, the demand regulator controls fuel flow based on engine vacuum. If the internal diaphragm has a pinhole tear, it allows too much fuel during deceleration, causing the engine to race before the governor catches up. Quick test: remove the vacuum line from the regulator with the engine off. If you see liquid fuel or smell strong LP, the diaphragm has failed. Replace the regulator as an assembly.
3. Check Governor Springs
On Kohler models with mechanical governor systems, inspect the governor springs. A broken or stretched spring won’t provide the correct counter-tension on the governor arm, causing RPM hunting that can escalate to overspeed. Replace springs in matched sets.
4. Verify Controller Output to Actuator
With the engine running at steady speed, use a multimeter to check the actuator control signal. A healthy Kohler Decision-Maker controller sends a varying DC signal to the actuator — typically 0-10V or 4-20mA depending on model. A flat signal (0V with the engine running) indicates a controller fault. Also check the wiring harness for damage — rodent damage is common on standby units.
Parts Reference
| Part | Part Number | Cost |
|---|---|---|
| Governor actuator (residential) | Kohler A-435316 | $150-$300 |
| Governor actuator (industrial) | Kohler A-467924 | $200-$400 |
| Demand regulator (NG/LP) | Kohler A-256914 | $80-$150 |
| Governor spring set | Kohler A-238590 | $15-$30 |
| Actuator linkage kit | Kohler A-435320 | $20-$40 |
Need Replacement Parts?
Before ordering, match the generator part to the model number, electrical rating, and failure symptom. Check current prices on Amazon - prices and availability change frequently.