Display shows FLO or FL1 and heater will not run; may show intermittent heating.

Safety first: Turn off power at the GFCI breaker before opening the equipment bay or loosening any unions.

• 1. Check water level: Ensure the spa is filled to the proper level. Low water can cause suction of air and low flow.
• 2. Clean or remove filters: Take out all filters and rinse thoroughly. For testing, run the spa briefly with filters removed. If FLO clears, replace or deep-clean the filters.
• 3. Bleed air from pump: Loosen the union on the circulation pump or main pump until air and water escape, then retighten. This removes trapped air that can prevent flow.
• 4. Inspect flow switch: Locate the flow or pressure switch on the heater manifold. Check that its wires are firmly connected to the PDC Spas control board. Look for kinks or blockages in the plumbing near the switch.
• 5. Test pump operation: With power restored, listen for the circulation pump running. If it hums but does not move water, the impeller may be jammed or the motor failing. In that case, replacement of the pump assembly is usually required.
• 6. Replace flow switch if needed: If flow is clearly strong but FLO persists, the flow switch may be stuck open. With power OFF and water level lowered if necessary, remove the flow switch from the heater manifold and install a compatible PDC Spas flow/pressure switch, using new seals.

Do not bypass the flow switch as a permanent solution; it is a critical safety device. If you are unsure, contact a qualified spa technician.