AO Smith gas valve clicks but no gas, won't stop cycling

mgbinsk

I have an AO Smith natural gas water heater (model: GPHE50 Series 100) 50 gallon capacity. Today I noticed the blower fan was running over and over, so I went to take a look. We had been using hot water earlier in the day so I know it was working up to that point, but it was strange that the fan would run and then stop repeatedly as I thought most units stop after three failed attempts and then display an error code if there's a problem. The control valve assembly would click a couple times and all the LEDs would flash, the fan would power up and you can see in the little window at the bottom that the igniter would start to Glow, then there would be a click but no Flame, and then the igniter would turn off and the fan would turn off. Then this cycle repeats itself and it continues to do so as long as there's electricity to it. It just doesn't stop, so there is no error codes for me to get an idea of what's Happening but my suspicion is it's the control valve which I assume has the gas valve inside it. I know our natural gas service is on because other appliances are functioning which also use natural gas. Any ideas on how I can troubleshoot this?

EBEBRATT-Ed

Yes. Check for power to the gas valve. That's the first step. If you have power the most likely problem is a bad gas valve although it could be something else

HVACNUT

Is there a wiring diagram on the tank so you can post a pic of it? There might be a rollout or flammable vapor sensor open preventing 24v to the gas valve.

mgbinsk

Local supplier wouldn't sell a control valve to me because I'm not a licensed gas fitter, had a plumber get the part (one day wait to bring in from other province), plumber installed and confirmed the control valve was faulty, but the flame sensor is ALSO showing error code (which is strange because the entire ignitor and flame sensor assembly was replaced 6 months ago). Had to order that part the following day. We are now on day 7 without hot water because of our LEMON water heater. Hopefully the flame sensor is the only problem remaining, but now I'm worried that we are approaching the end of our 6 year warranty period and we will be stuck with this piece of junk afterwards.

HVACNUT

It's not just a simple thermocouple on the water heater? If it is you can pick one up at the hardware store.

mgbinsk

No this unit has an ignitor, not a pilot light. The ignitor and flame sensor are both part of one assembly unit along with the the gas supply tube.

mgbinsk

New flame sensor fixed the problem, now have a working water heater. Thanks to everyone who offered help