Hayward Pool Heater AO / AC Error Code

Updated 2026-08-30 · review status: manual-verified · reviewed by MiniSplitDecoder Editorial Team Last verified: 2026-08-30

Check your model first

The source record does not specify an exact model family.

Match the model on your equipment label to the linked manufacturer documentation. The same code can mean different things across model families.

Quick answer

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 running or running weakly, vacuum switch tubing blocked/cracked/disconnected, vent restriction or improper venting configuration, failed vacuum switch. Check that blower motor spins freely and runs when called. Inspect vacuum switch tubing for crack

Severity: high · DIY difficulty: easy

Safety

Stop at the exterior: power-cycle at the disconnect, clean the filter/basket, and check for obvious water-flow blockage. Pool heaters combine gas piping, 240 V wiring, and (on heat pumps) refrigerant — burner, control-board, and sealed-system work requires a licensed technician. If you smell gas, shut the gas valve and leave the area first.

What AO / AC means

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 running or running weakly, vacuum switch tubing blocked/cracked/disconnected, vent restriction or improper venting configuration, failed vacuum switch. Check that blower motor spins freely and runs when called. Inspect vacuum switch tubing for cracks, kinks, or blockages. Verify vent termination is clear of debris or bird nests. Test vacuum switch with manometer if available.

First checks before service

This page currently documents the safe reset triage. If the code returns, use the linked source manual or a qualified technician for code-specific diagnosis.

  1. 1. One-time fault event (power disturbance or transient sensor reading) common DIY

    Check: Power-cycle at the breaker/disconnect (or unplug for CPAP), restore, and run the system while watching for the code.

    Fix: If the code does not return after a full run cycle, the fault was transient — monitor, no repair needed.

  2. 2. Fault persists after a clean reset occasional pro only

    Check: If the code returns immediately or every session, note the conditions (startup, heating, after rain).

    Fix: A persisting code points at the component the manual assigns to this code — that repair is technician territory.

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Sources

Related Pool Heater guides

Hayward Pool Heater Error Codes: Safe Checks