Hayward Pool Heater Error Codes
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Featured codes
- AO / AC — Blower Vacuum Switch Error AO means vacuum switch won't close (no air movement detect
- bD / EE / CE — Control Board / Communication Errors Control board or display communication errors. E
- HF — Flame Present / Gas Valve Off Flame detected when gas valve should be closed—serious
- HS — High Temperature / Rapid Rise High return water temperature or rapid temperature rise
- IF / IO — Ignition Failure Ignition failure during startup sequence. Heater clicks, blower runs
- LO — Safety String Open / Low Pressure Safety string open—water pressure switch, limit swi
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Model families
Safe checks with an external tool or supply
These pages list the check you can do from outside the unit, with an optional external tool or maintenance supply. None of them repair an internal fault.
Other pool-heater references
The same fault families appear across brands:
Related troubleshooting guides
Manufacturer manuals
A codes
- Hayward AO / AC error code
Blower Vacuum Switch Error AO means vacuum switch won't close (no air movement detected). AC means vacuum switch won't open (stuck closed). Blower not…
B codes
- Hayward bD / EE / CE error code
Control Board / Communication Errors Control board or display communication errors. Erratic display behavior, random codes, or blank segments. Damaged…
H codes
- Hayward HF error code
Flame Present / Gas Valve Off Flame detected when gas valve should be closed—serious safety condition requiring immediate attention. Shut down heater … - Hayward HS error code
High Temperature / Rapid Rise High return water temperature or rapid temperature rise detected. Heater starts, runs briefly, then shuts down. Low flow…
I codes
- Hayward IF / IO error code
Ignition Failure Ignition failure during startup sequence. Heater clicks, blower runs, but never lights. No gas supply or gas pressure too low, weak o…
L codes
- Hayward LO error code
Safety String Open / Low Pressure Safety string open—water pressure switch, limit switch, or vent pressure switch not satisfied. Heater refuses to sta…
P codes
- Hayward PF error code
Power Fault / Low Voltage Supply voltage polarity reversed or voltage too low. Heater will not fire. Hot and neutral wires reversed, voltage drops bel…
S codes
- Hayward SF error code
Temperature Sensor Failure Temperature sensor (thermistor) input failure. Temperature reading wildly inaccurate or missing. Failed thermistor, damaged…