Pump stops during operation and displays F4, often on hot days or after running for several hours.

Safety: Isolate power before touching the motor housing; it may be very hot.

• Allow cooling: Let the pump sit powered off for at least 30–60 minutes to cool down.
• Clean ventilation: Brush or vacuum dust, cobwebs, and debris from the motor cooling fins and fan cover. Ensure the rear fan on the Hurlcon motor spins freely.
• Check system backpressure: Backwash or clean the filter (sand, cartridge, or DE) to reduce load on the pump. A dirty filter increases motor current draw.
• Improve airflow: Ensure the pump is not enclosed in a sealed box. Provide ventilation openings or leave doors open when running.
• Restart and monitor: Restore power and run the pump while monitoring motor temperature by touch (should be warm, not too hot to touch for more than a second).

If F4 recurs frequently, the Hurlcon motor’s internal thermal cut-out or windings may be failing and the motor should be tested and possibly replaced.