5 Year Old A.O. Smith 50 Gal Gas Water Heater Won't Heat Regularly

[hoffacard]

:wall:PLEASE HELP! I have been having problems with my water heater for several weeks now. At first I noticed we had no hot water one morning. I unplugged it-plugged it back in and it came on and worked fine for a day or so. It has worked off and on by me doing this. Well...now it comes on, but wont stay on long.It comes on as normal (The blower motor comes on, I hear a click then the burner lights),but then the burner goes out. It goes through the starting cycle 4 times before finally shutting off. The green light on the temperture control box flashes 6 times. Thanks

[mbk3]

Sounds like a rectification problem.. Try cleaning the flame rod. I am not familar with this unit. Does it have a pilot or hot surface igniter?? If pilot make sure clean and striking flame rod

[brianhatchl]

hoffacard,

I'm having this same problem with my A.O. Smith FPSH-50 hot water heater, did you ever find the fix and can you share the details with me?

Here are the details of my problem:
I have a ~6 year old A.O. Smith FPSH-50 gas water heater. This is a power vent unit with electronic ignition. The burner was running fine (as needed) until today...

...the TPR valve was leaking intermittently and the water pressure gauge I attached indicated no sign of high pressure (above 80 psi). I replaced the TPR valve and when I turned the gas and water supply back on and then set the thermostat to "hot" and turned the power on, the burner ignites, but will not stay lit.

When the power is turned on, the power vent blower starts and runs for a bit. The hot surface igniter heats up and glows orange. Then there is a click and gas flows, is ignited, and burns for a half second and then another click seems to cut off the gas supply and the burner goes out. The water heater cycles through this 4 times before giving up. The green light on the thermostat is blinks 6 times and then blinks 4 times. Any ideas what I could have screwed up during the TPR valve replacement? The thermostat did get a little wet because I didn't drain the tank enough before removing the valve and a few cups of water drained down the side, but the thermostat control was definitely NOT submerged.

thanks in advance,
Brian

p.s. as this is a do-it-yourself project, against my wife's better judgement, i hope to get this resolved before she gets home or at least before she needs a shower tomorrow morning.

[somehvacguy]

It sounds to me like you have either a problem with the air pressure switc or the tubing that leads to the induction blower. Moisture develops inside the tubing or the nozzle that sticks out of the induction fan or the air pressure switch. The light blinking are error message usually there is a trouble shooting guide either posted right on the unit or in the user manual and this will guide you in the right direction. If neither are found, you can go to the Ao Smith website or call the manufacture directly. I hope I have given some direction in your problem.

[brianhatchl]

somehvacguy,

Thanks for the reply. I did find a service manual on the A.O. Smith website. I went through some troubleshooting steps and everything checks out. According to the "SmartValve" sequence of operation, once the main burner ignites, the flame must be sensed within 4-5 seconds or the gas valve is "de-energized" and the cycle is tried again three more times before giving up. Also, the "SmartValve" will try to reset itself every hour once it's in this "lockout state" (that's what the 6x blinking led indicated). This afternoon I was turning it on to observe the operation sequence and then when it failed, I'd turn it off to troubleshoot. Around dinner time I left it alone, but turned on for a while and before bed I went down to check on it and the blower was running and the burner was heating away. I'll see if we have hot water tomorrow morning, but for now it seems the mystery has solved itself, though I don't understand why.

Thanks again for the advice, it kept me from giving up, though in the end that's what seemed to do the trick.

Brian

[mundlin]

hoffacard,

Eventually it will fail and I can say with 95% certainty it's a dirty flame sensor. Unplug the water heater, remove the door at the bottom and then take out all of the screws around that observation window and the gas inlet pipe, on mine it was 7 screws. Now pull out the burner, attached is the igniter and flame sensor. On this pic, the flame sensor is the metal rod on the right:
http://bestbuyheatingandairconditioning.com/Merchant2/graphics/00000001/hsi83267.jpg

Get a piece of 60 grit sand paper and sand until it's nice and shiny, especially the tip. Reverse the process and plug it back in. Wait 1 hour and enjoy a nice hot shower!

It's a piece of maintenence that most water heaters and furnaces need occasionally, like brake pads on a car, nobody expects them to last forever.

BTW, it might be a nice service reminder that if you need to clean it every 5 years, to also replace the annode rod at the same time and drain the tank to clear out any sediment, it will increase the life of your water heater significantly!

[Feester]

I would like to thank you for the tip. I sanded the tip of the flame sensor rod and put it back in and it fired up without any problems. Your post saved me a ton of time because I was constantly fighting the stupid thing.

[mundlin]

I failed to mention that you need to shut off the gas, and also that you need a large open end wrench, I think 3/4", in order to remove the burner, but I assume you figured that out.