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Rick, Construction Supervisor
Category: Plumbing
Satisfied Customers: 19069
Experience:  Licensed Master plumber with 40+ yrs. experience.
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How do you reset an AO Smith water heater the light is stuck

Resolved Question:

How do you reset an AO Smith water heater? the light is stuck on FV sensor detects the presence of flammable vapors. I put a new sensor on as the first one got wet and I dried it with a hair dryer. I cannot clear the message now and I know there are no flammable vapors because I have two water heaters side by side and the other one is working fine.
Submitted: 7 years ago.
Category: Plumbing
Expert:  Rick replied 7 years ago.
HiCustomerbr />You reset the unit by powering it down (unplug it) waiting several minutes then power it up again. It is quite possible that you have a faulty gas control valve. Since you changed the part indicated to be at fault and still have the same error then the most likely source of the error now is the micro-processor in the valve.
Customer: replied 7 years ago.
This doesn't work. I unplugged it for 10 hours and when I plugged it back in and turned on the fan, the water heater control gave the same message and is locked out. I just need to get the water heater control reset so I can get the heater working again. It is still locked out and I have an identical water heater next to it that is working fine.
Expert:  Rick replied 7 years ago.
You may need to replace the gas control valve. Given your description it is likely that the control valve has failed. If the unit is less than 6 years old you may have a warranty claim.
You can contact AO Smith at
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