FS
Hayward
Flame Sense Fault
Heater displays FS and will not fire; may occur after ignition attempt.
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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 or oxidized flame sensor, Poor burner ground, Reversed polarity on power supply, Weak flame due to low gas pressure
How to Fix / Troubleshooting
Safety First: Turn off power and gas before removing burner or sensor components.
- Clean flame sensor: Locate the flame sensor rod near the burner flame. Remove it and gently clean with fine steel wool to remove oxidation. Reinstall securely.
- Check ground connections: Ensure the burner tray and control board ground wires are tight and free of corrosion.
- Verify line polarity: Using a meter, confirm that hot and neutral are correctly wired at the heater's power connection. Incorrect polarity can affect flame sensing.
- Observe flame: After reassembly, restore gas and power, then call for heat. Observe the flame through the sight glass. Weak or unstable flame indicates a gas supply or burner issue that may require professional service.
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Repair Difficulty
Hard
4/5
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