For the last week the pilot on the A O SMITH water heater has been going out. and is VERY difficult to get lite againI have only the information given to me by my tenant as the heater is not in my house.The plumber has been over 3 times and my husband several and can not find the cause.Any suggestions.THANKS so muchbj
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Re: pilot goes out
IF THIS IS A STANDING PILOT TYPE WATER HEATER MEANING THE PILOT STAYS LIT ALL THE TIME IT IS USUALLY CONTROLLED BY A THERMOCOUPLE WHICH IS USUALLY THE CULPRIT THIS IS USUALLY AVAILABLE AT ANY GOOD HARDWARE STORE GET THE SAME LENGTH AS YOU TAKE OUT EX 12-18-24 INCH
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You have tank-type gas water heater with standing pilot light.
Instructions for lighting pilot light are usually on front of water heater. Since water heaters vary widely, if you want specific information without guessing, then add a comment with model number that appears on label on side of tank, and also describe the gas control valve on front of unit. This information will let expert located manual and look up specific information plus troubleshoot steps for that model.
The thermocouple has gone bad or in this case is going bad to the point that it is useless.
The thermocouple is the pilot's, well, co-pilot! It is the electronic device that senses if the pilot flame is hot enough to ignite natural gas or propane fuel to the burner. If the thermocouple thinks it's safe, then it keeps open the main gas valve located in the pilot assembly. If the thermocouple does not sense enough heat from the pilot flame (such as when the pilot is out), then the thermocouple shuts off the gas valve to the burners. How the Thermocouple Works So what is this thing and how does it work? Well the thermocouple (technically called a thermocouple junction) is a device that contains two metal wires welded at the ends and placed inside a protective metal case. The thermocouple sensor is found at the business end of the pilot flame and is designed to be placed in the hottest part of the flame. The other end is connected to the pilot valve body. As the thermocouple heats up, it produces a small amount of electricity and when it gets hot enough from the pilot, send a signal to open the gas valve by using a solenoid operated by a 24 volt transformer. The thermocouple calls the shots, and by converting heat to an electrical signal, it allows the gas valve to open or close.
Once the gas valve is open, gas is then constantly supplied to the pilot and as required for the gas burners (as called for by the thermostat). If the pilot goes out, then the thermocouple gets cold and produces no electric signal to open the gas valve's solenoid and the gas valve shuts off the gas supply to the pilot and burners. Neat huh?
It could be a thermocouple but first take the whole pilot assembly out and disassemble it. Clean it very good (compressed air is ok) especially the orifice inside the pilot horn. You may just have a weak pilot. If the flame is in good contact with the thermocouple and problem still exist, then change the thermocouple. I believe in doing the free things first.
The Cold air screen on the bottom of the water heater is partially plugged. That is if the pilot light can be lit and stay on, but goes out when the heater should be functioning normally. This is not the removable plastic screen but a round white-yellow grid with 1/32" holes. You can try to clean it through the bottom but you may have to remove the gas line from the controller to the burner, pilot gas line, and thermocouple connection to remove that complete assembly to get access to the screen. The AO Smith booklet warns of this but they pretend the plastic screen will keep this second screen clean but it won't. After three years it was two thirds plugged.
The thermocouple is the copper one the other is the gas supply to the burner check your flue pipe for restrictions see if a flame from a lighter sucks up the flue from the top hood you may need a new gas control valve
It sounds like your flame detector (usually a thermocouple) has gotten weak and when you cleaned the pilot the stronger flame was able to generate enough power to keep the gas valve working. If you replace the thermocouple your problem should go away. If a new thermocouple will not keep the gas valve operating...the coil in the gas valve has gone bad and you will need to replace the gas valve assembly. (most valves do not have replaceable coils).