Hayward GAS HEATER KEEPS GIVING ERROR AO blower vacuum switch error? is this an electrical problem or does it mean the switch went bad, what do i look for?

check gas pressure if not enough it will not run call gas company sounds like you need more pressure

ErrorAO means BlowerVacuum Switch Open. If the blower prover switch does notclose after the blower starts the control will stop the ignition trial go intolockout. The blower will continue to run. Automatic reset is immediate afterthe switch closes. So you need to check this.

Either the fan is not working, or the fan prover (pressure switch) switch is stuck. If you can hear the fan going strong, it is most likely the switch. You may try to just clean it out, but you may need a replacement.


This error is produced when the blower prover switch does not close after the blower starts, the control will stop the ignition and go into lockout. Automatic reset is immediate after the blower prover switch closes.

If you keep having this problem, contact a reputable service company, especially if it's under warranty.

The link to the owners manual is below, it references fault codes, etc..

Hope this helps.

http://74.125.95.132/search?q=cache:4mAdY7bLfoQJ:www.haywardnet.com/products/Manuals/pdfs/Manual227.pdf+hayward+AO+error

You didn't indicate exatctly which model you have. But on most the AO error code is :Blower vacuum switch
open error If the blower prover switch does not close after the blower starts the control will
stop the ignition trial go into lockout. The blower will continue to run. Automatic reset is immediate after the switch closes.Check to be sure combustion blower starts
If you don't have your manual you can download one for your exact model at : www.haywardnet.com

Check the tubing going from the blower to the blower vacuum switch. If there are any cracks, missing, or cut, it will give the same code. Rodents like to chew on this tube. Also, if the blower is not coming on at all, then you will get the same code, and the problem is not with the switch, it is likely in the blower.

AO will apply to your blower, blower tubing, or blower vacuum switch. You need to check these items.

You need to check and see if you have enough gas supply to run the heater. Older heaters would run on a small gas supply but forced draft are hinkey about how much gas they get. Sometimes this is a gas line size problem but more often than not it will be a gas meter problem. On the face plate of your meter their is a number that tells the size. With a 250 and other appliences in the house you will want a 350 or bigger. The good news is the gas company will upsize this for nothing. If they are supplying more gas your buying more gas. It could be other things but this is the first thing to look into.

This error is produced when the blower prover switch does not close after the blower starts, the control will stop the ignition and go into lockout. Automatic reset is immediate after the blower prover switch closes.

If you keep having this problem, contact a reputable service company, especially if it's under warranty.

The link to the owners manual is below, it references fault codes, etc..

Hope this helps.

http://74.125.95.132/search?q=cache:4mAdY7bLfoQJ:www.haywardnet.com/products/Manuals/pdfs/Manual227.pdf+hayward+AO+error&cd=7&hl=en&ct=clnk&gl=us