Generator runs for several minutes then shuts down with HIGH COOLANT TEMP or ENGINE OVER TEMP alarm.

Safety first: Shut down the generator, disconnect battery negative, and allow the engine to cool fully.

Steps:

• Inspect radiator and airflow: Open the enclosure doors. Check the radiator fins on your Gillette standby generator for dirt, leaves, or debris. Clean gently with low-pressure compressed air from the inside out or with a soft brush. Ensure louvers and intake/exhaust openings are not blocked.
• Check radiator fan operation: On air-assisted liquid-cooled models, start the unit and observe if the electric fan engages as temperature rises. If the fan does not run, test the fan fuse, fan relay, and fan motor. Replace the failed component.
• Verify coolant level: Low coolant can cause false high-temp readings. Top off as per the LOW COOLANT procedure.
• Check water pump and belt: Inspect the water pump drive belt (if belt-driven) for tension and wear. Replace if cracked or loose. Look for coolant seepage at the water pump weep hole indicating pump failure.
• Thermostat issues: If overheating persists with good airflow and coolant level, the thermostat may be stuck closed. Replacement requires draining coolant and removing the thermostat housing; this is best done by a technician.