Poolex pool heat pump runs briefly then shuts down with F3 error on display.

Safety: Turn off the Poolex heater before working on pool plumbing. Do not run the heater without water flow.

Steps to restore flow:

• Verify pump operation: Make sure the pool circulation pump is primed and running. Check for air bubbles in the pump basket indicating suction leaks.
• Open valves fully: Confirm that inlet and outlet valves to the Poolex heater are fully open. If a bypass is installed, adjust so that most of the flow passes through the heater as per Poolex guidelines.
• Clean filters: Backwash sand filters or clean/replace cartridge filters. Clean skimmer and pump baskets.
• Bleed air: If your system has air bleed valves near the Poolex heat pump, open them briefly to release trapped air.
• Inspect flow switch: Locate the Poolex flow switch in the water line (usually near the inlet). Check for debris around the paddle or turbine by removing the union (close valves first). Clean gently and reinstall.
• Reset unit: Restore power and clear the F3 error from the control panel. Confirm that the heater now runs continuously.

If F3 persists despite good flow and a clean system, the flow switch or flow sensor may be faulty and should be tested and replaced by a technician.