Display shows FL1, spa does not heat and may shut down the heater circuit.

Safety: Turn off power at the GFCI before removing panels or disconnecting any components.

• Confirm water level and jets: Ensure water is at the proper level and all slice valves and diverter valves are fully open. Closed valves can starve the heater of flow.
• Clean filter and check suction: Remove and rinse the filter cartridge. Inspect skimmer baskets and suction fittings for debris. Run the spa briefly without the filter to see if FL1 clears.
• Bleed air: With power OFF, loosen the union on the circulation pump or heater manifold to release trapped air. Retighten once water flows steadily.
• Inspect flow switch: Locate the flow switch on the heater manifold (usually a tee with two small wires). Check for loose or corroded connectors. If accessible, gently tap the body of the switch to free a stuck paddle or plunger, then restore power and test.
• Electrical test (advanced): With power OFF, disconnect the flow switch leads from the control pack and test continuity with a multimeter while water is flowing (pump running). The switch should read closed (near 0 ohms) when there is flow. If it remains open, the switch is defective.
• Call a pro: If the switch tests bad or the control board is not reading a good switch, contact a Hydropool service technician for replacement and calibration.