Generator starts but quickly shuts down with OVERSPEED alarm; engine may rev unusually high just before shutdown.

Safety first: Switch the Guardian controller to OFF and open the main line circuit breaker. Do not run the unit again until the cause is identified.

• Inspect throttle and governor linkage: With the engine off, open the enclosure and manually move the throttle plate and governor linkage. They should move smoothly without binding. Clean any dirt or corrosion and lubricate pivot points lightly if recommended by Guardian.
• Check speed sensor connection: Locate the engine speed (RPM) sensor on the flywheel housing or crankcase. Ensure the connector is fully seated and free of corrosion. Inspect the harness for chafing or broken insulation.
• Look for wiring damage: Trace the harness from the engine to the Guardian control board. Repair any pinched, cut, or rodent-damaged wires.
• Controller reset: After inspection, clear the alarm by placing the switch to OFF for 30 seconds, then back to AUTO. Perform a manual test. If OVERSPEED persists, the speed sensor or governor module likely needs replacement and calibration by a technician.