Engine Overspeed Shutdown Detected

Common Symptoms

• Generator starts but immediately shuts down within seconds of reaching run speed
• Panel displays fault code 19 on the RDC2 controller display panel
• Red fault light is illuminated on the generator control panel
• Engine sounds like it is surging or racing before shutdown
• Generator will not return to AUTO or RUN mode until fault is manually cleared
• Unit may attempt to crank and restart, then shut down again on repeated start attempts
• OnCue Plus monitor or Mobile Link app shows a critical overspeed alarm

Probable Causes (Ranked by Likelihood)

• Governor failure or misadjustment allowing RPM to spike above 63-65 Hz threshold Very Likely
• Fuel system delivering excess fuel due to sticking or failed carburetor or gas valve Very Likely
• Throttle linkage disconnected, binding, or stuck in a partially open position Likely
• Failed or faulty magnetic speed pickup sensor sending incorrect RPM signal to the RDC2 controller Likely
• Engine load suddenly dropped to zero (load disconnect) causing a brief unloaded overspeed event Possible
• Low engine oil or coolant condition forcing a simultaneous shutdown that is misread as overspeed Possible
• RDC2 controller fault or corrupted calibration causing false overspeed trip at normal operating RPM Less Likely

Step-by-Step Diagnostic Procedure

1. Step 1. Press the OFF button on the panel to clear the active fault, then note whether the fault code 19 returns immediately on the next start attempt or only after the engine reaches full speed. If it trips before the engine fully ramps up, suspect a speed sensor or controller issue.

2. Step 2. Inspect the throttle linkage and governor arm visually with the generator OFF and the battery disconnected. Look for a broken cotter pin, disconnected rod, or binding pivot. Move the governor arm by hand to confirm it moves freely through its full range.

3. Step 3. Check the fuel supply pressure at the gas valve inlet using a manometer or LP gauge. For NG supply, confirm pressure is 5-7 inches water column at the regulator outlet. Excessive fuel pressure can force the engine to overspeed. If you do not have a manometer, call a gas technician.

4. Step 4. Locate the magnetic speed pickup sensor, typically mounted near the flywheel ring gear on the engine block. Inspect the sensor tip for cracks, corrosion, or debris buildup. Using a multimeter set to AC millivolts, measure the sensor output at cranking speed. A healthy sensor should produce 0.5 VAC or more. A reading near zero indicates a failed sensor.

5. Step 5. Measure the air gap between the speed pickup sensor tip and the flywheel ring gear teeth. The typical Kohler spec is 0.030 to 0.050 inches (0.76 to 1.27 mm). An air gap that is too large produces a weak signal; too small can cause false readings. Adjust by threading the sensor in or out and re-locking the jam nut.

6. Step 6. With the generator running normally (if it will stay running long enough), use a tachometer or the RDC2 controller display panel to observe the actual engine RPM. Normal operating RPM for a 60 Hz residential unit is 3,600 RPM. A reading above 3,780 RPM under no load indicates a real overspeed condition, not a sensor false alarm.

7. Step 7. If the engine RPM is confirmed high and the throttle linkage is intact, the governor itself is the likely culprit. Kohler air-cooled engines use a mechanical flyweight governor that can wear or lose spring tension over time. Governor adjustment requires a tachometer and specific Kohler service procedures. At this point, call a certified Kohler service technician.

8. Step 8. If all physical components check out and the engine RPM appears normal on the display, the RDC2 controller may need a software update or recalibration. Contact your Kohler dealer to connect a Kohler service laptop and run controller diagnostics.

Frequently Asked Questions