AO
Hayward
Air Flow / Air Pressure Switch Open
Display shows AO; blower may run continuously or not start; heater will not fire.
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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
Blocked exhaust or intake venting, Failed air pressure switch, Cracked or disconnected air tubing, Blower not running or running too slowly
How to Fix / Troubleshooting
Safety First: Turn off power and gas. Do not operate the heater with a blocked vent or bypassed safety switches.
- Inspect venting: Check the flue outlet and intake (if applicable) for nests, leaves, or obstructions. Clear any blockage.
- Check blower operation: With power restored, call for heat and observe if the blower starts. If it hums or does not spin, the blower motor or capacitor may be faulty.
- Inspect air pressure switch tubing: Turn power off again. Locate the air pressure switch and its rubber tubing to the blower housing. Ensure the tubing is not cracked, kinked, or disconnected.
- Test air pressure switch: Verify wiring connections. If the switch does not close when the blower runs and venting is clear, replace the air pressure switch with a Hayward-compatible part.
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Repair Difficulty
Hard
4/5
Required Part
Air Pressure Switch
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