FLO
Coast Spas
Insufficient Water Flow / Flow Switch Open
Display shows FLO or FL and heater will not run; may also show intermittent heating and flow-related shutdowns.
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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.
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Possible Causes
Dirty Coast Spas filter cartridge restricting flow, Air lock in circulation pump, Faulty flow switch or pressure switch, Weak or failed circulation pump
How to Fix / Troubleshooting
Safety first: Turn off power at the breaker before removing filters or opening unions.
- Clean or remove filter: Take out the filter cartridge and run the spa briefly without it. If FLO clears, replace or deep-clean the filter.
- Bleed air from pump: Loosen the pump union on the suction side slightly until air escapes and water dribbles out, then retighten. Repeat on discharge side if needed.
- Check for strong circulation: With power on, verify a steady stream from the circulation return. If weak or pulsing, the circulation pump may be failing or blocked.
- Inspect flow switch: Locate the flow or pressure switch in the heater plumbing. Ensure wires are firmly connected and there are no kinks in nearby hoses. Do not adjust factory calibration screws.
- Bypass test (for diagnosis only): A qualified person may temporarily jumper the flow switch leads to confirm diagnosis. If FLO clears and heat starts, replace the flow switch. Never leave the spa operating with the switch bypassed.
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Repair Difficulty
Medium
3/5
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