Hayward Heater AO Code: Causes and Fixes

Q: I’m dealing with an AO code on my Hayward heater. Could you explain how the heater works and guide me through diagnosing and fixing this issue?
– Alex Hall

The Hayward Heater AO Code occurs when the blower vacuum switch does not close after the blower starts, when the blower switch opens unexpectedly during the operation, or when the blower prover switch opens during the post-purge cycle (when the heater is not firing).

A: (From Tim David, Owner of Airlucent) Of course, I’d be happy to help! Dealing with a heater issue can be frustrating, but I’ll walk you through the process step by step. Let’s start with a bit of background on how your Hayward heater’s switch operates. When your blower is running correctly, it creates a negative pressure inside the blower housing. This pressure is crucial as it closes the contacts on the blower vacuum switch. This action is like a green light for your ignition control board, signaling that it’s safe to ignite.

Now, onto tackling that pesky AO code. Here’s a detailed guide:

Understanding Common Causes and Fixes:

  1. Vacuum Switch Tubing Faulty: This tubing is vital for proper switch operation. If it’s damaged or worn out, it needs replacing.
  2. Faulty Vacuum Switch Wiring: Wiring issues can be tricky. Ensure all connections are secure and there’s no visible damage.
  3. Blower Wiring/Connection Issues: A loose connection here can stop the whole show. Make sure everything is snug and in place.
  4. Defective Vacuum Switch: This is a bit more technical. You’ll need to measure the resistance on the blower windings.
  5. Bad Blower Relay: Here, you’re checking for 120VAC at the blower relay endings. No voltage? You might need a new relay.
  6. Overall Vacuum Switch Defect: If all else fails, the switch itself might need replacing.

Step-by-Step Diagnosis and Fixes:

  1. Safety First: Before you do anything, ensure your heater’s power is completely off. Safety is paramount here.
  2. Inspect the Vacuum Tubing: Look for any cracks, wear, or disconnections. If it looks compromised, replace it.
  3. Check the Vacuum Switch Wiring: Examine the wiring for any signs of damage or loose connections. Secure anything that seems out of place.
  4. Blower Wiring and Connection: Give your blower wiring a thorough check. Any loose plugs or suspicious-looking wires? Tighten and secure them.
  5. Vacuum Switch Inspection: If you’re comfortable using a multimeter, measure the resistance across the blower winding. The readings should be within the specified range (Red-to-White: 4 to 5 ohms).
  6. Blower Relay Check: This step involves a bit more technical know-how. You’ll need to measure for 120VAC across specific pins during the pre-purge period. If there’s no voltage, the relay might be the culprit.
  7. Vacuum Switch Replacement: If you’ve reached this step, it’s likely your vacuum switch needs replacing. This involves disconnecting wires, removing the old switch, and installing a new one. Remember to turn off everything before starting this process.

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Additional Tips:

  • Take Notes: As you go through each step, jot down what you find. This can be helpful if you need to call in a professional later.
  • Stay Organized: Keep your tools and replacement parts organized. This makes the process smoother and less stressful.
  • Patience is Key: Some of these steps can be intricate. Take your time and don’t rush.

By carefully following these steps and additional advice, you should be able to effectively diagnose and resolve the AO code issue on your Hayward heater.

Have a question about pool heaters? Airlucent owner Tim David would like to answer your question in an upcoming article, call (256) 399-9708 or contact David via the contact page.

Final Thought

When you are faced with a Hayward AO code, the above-mentioned issues are the commonest cause of the problem. Going through these troubleshooting steps should solve the problem. However, to keep your pool heater working in great condition, you need to observe regular maintenance. At least twice a year.

Having said that, if you are not familiar with the maintenance and repair of your heater, it’s best to call in a professional to come and give a hand. We hope you have resolved this problem though and thanks for reading.

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