Display shows FLO or FL1 and heater will not run; spa may show "Heating Suspended"
Safety Warning
This repair may involve working with high voltage components or water connections. Always unplug the appliance before removing any panels.
If you are not confident in your ability to perform this repair safely, we strongly recommend contacting a professional technician.
Possible Causes
How to Fix / Troubleshooting
Safety first: Turn off power at the GFCI breaker before working on plumbing or electrical connections.
Steps to resolve FLO/FL1:
- Check water level: Ensure water is at the proper fill line, typically above all skimmer openings and jets.
- Remove and clean filters: Take out the Strong Spas filters and rinse thoroughly. Try running the spa briefly without filters after restoring power. If FLO clears, replace the filters.
- Bleed air from pumps: With power OFF, loosen the union on the circulation pump and primary jet pump until air and a small amount of water escape, then retighten.
- Inspect the flow switch: Locate the flow switch in the plumbing near the heater. Check the wiring connection at the control pack for corrosion or loose terminals. Ensure the switch body is installed in the correct flow direction.
- Test the flow switch (advanced): With power OFF, disconnect the flow switch from the board and temporarily jumper the two flow switch terminals. Restore power briefly. If FLO disappears and the heater engages, the flow switch is likely faulty and should be replaced. Do not leave the spa running with the jumper installed; this is for testing only.
- Evaluate circulation pump: If there is little or no water movement at the heater return, the circulation pump may be weak or seized and require replacement.
When to call a technician: If replacing filters and bleeding air does not restore flow, or if you are not comfortable testing the flow switch electrically, contact a spa technician.