Liquid-cooled Generac standby generator shuts down with 'High Coolant Temp' or 'High Engine Temp' alarm after running under load.

Safety: Allow the engine to cool completely before opening the coolant reservoir or radiator cap. Hot coolant can cause severe burns.

• Check coolant level: Inspect the overflow reservoir and radiator (if accessible). Top off with the correct coolant mixture recommended by Generac. Do not mix incompatible coolant types.
• Inspect radiator and airflow: Remove debris, leaves, or dirt from the radiator fins and generator louvers. Ensure there is adequate clearance around the generator for airflow per installation guidelines.
• Verify fan operation: Start the generator in MANUAL and observe the radiator fan. If it does not run when the engine warms up, check the fan relay, fuse, and wiring. Replace the electric fan or fan clutch if defective.
• Check thermostat and pump: If overheating persists, the thermostat may be stuck closed or the water pump may be failing. Replace the thermostat first; if no improvement, inspect and replace the water pump as needed.