Water Heaters - thermostat, thermocouple, or over heat saftey switch

I have a fairly new (3 years old) gas water heater that won't stay lit. If the water inside is cold the pilot and subsequently the burner WILL light. When the water gets to temperature, the burner goes out and so does the pilot light. I can then get the pilot to light as I depress the button, but it goes out as soon as I let go of the button. Occasionally if I have gotten the tank hot, I can get the pilot to stay lit if I set the temperature in the warm/vacation area.
So, does this sound like the thermocouple, thermostat, or could it be the safety switch meant to turn it off if something( I'm not sure what) gets too hot? I've looked it up and there is supposed to be a button to push to reset the switch, but the only thing on it that I can find that could somehow be seen as a button, doesn't push.

Any help anyone could give would be greatly appreciated.
thank you

Brother Dave

It sounds like the pilot burner and pilot orifice are dirty.

If you look carefully you will very likely see that the pilot flame is soft and easily blown around --- and out. It should burn sharp and blue like a small blow torch.

The pilot burner needs to be removed and disassembled and the pilot orifice (which has a small hole to form the pilot burner gas jet) cleaned with a wire from a wire brush.

Remember, thermocouples are cheap and not too hard to replace. Start there. Check your pilot orifice at the same time.

I will clean it this afternoon. I am curious as to how the symptoms I described would indicate that the burner and orafice are dirty.

The pilot flame may be too low causing not quite enough milivolts to be produced, telling the valve to open or even keep the pilot lit.

People can, of course, choose to replace the thermocouple if they wish.


But in the case here, where the water heater pilot will stay lit for a while but shuts off after the burner has operated, it's unlikely that the thermocouple is a problem --- let's say a 5% probability.

That means that if it takes the avearge DIYer an hour to shop for a suitable thermcouple and the part costs $10, then you would have to spend TWENTY HOURS of time and $200.00 replacing these parts before finding one that corrected the problem.

Replacing thermocouples willie nillie is a mark of a poor repairman, in my opinion. Thermocouples are actually a pretty reliable part.

The correct way to test a thermocouple is to measure the voltage produced while it's powering the gas valve magnet --under load. That allows the repairman to discriminate between a bad thermocouple and a bad gas valve magnet.

But it would be a rare DIYer who would have the fitting needed to perform that test. In the case described here though, I'd say it's unlikely that the thermocouple is the problem, and spending the time and money to replace it would be time and money wasted.

But again, people can do what they choose.

I agree, SeattlePioneer...

that it could be a dirty pilot orifice. But I, nor you, are there to see the pilot flame to make any accurate decisions. All we can do is speculate.

Almost every hardware store I have ever been to carries an approximate $10.00 part called a thermocouple. Most times, it will take all of 5 minutes to go purchase one.

When removing the pilot assembly to check or clean the pilot orifice, you will also need to remove the thermocouple at the same time. Doesn't that seem like a good time to replace the $10.00 part while you have the assembly removed from the water heater just in case of a 5% chance, that it may be the answer to solve the problem. Or is it better in your opinion to have to take the assembly apart twice, (which sometimes can be a real pain in a##), once you find that it may not be a dirty pilot?

I am only trying to help the average homeowner save a few steps and possibly solve the problem in the interim with a low cost.

You are trying to help and not even mentioning to be very careful when cleaning the pilot orifice as to not enlarge the orifice size, or there may be more problems.
You have also failed to mention that this could be caused by a negative pressure in the home or a down draft in the chimney. It could even be an electrical problem depending on the type of gas valve and or limit switches the water heater has. Do we know if this water heater is an older style or an FVIR type water heater?

There are still a lot of possibilities that could be the reason, but I was trying to start with the easiest items.

You are correct, People can, of course, choose to just clean the pilot orifice.

Thank You, Mark

I recommend cleaning pilot orifices with the wire from a wire brush. I've never seen damage to a typical pilot light from that yet.

The draft diverter at the top of the water heater should prevent down drafts from affecting the burner or pilot. It would be rare for that to be a problem if the draft diverter is installed, in my experience.

For the same reason, negative pressure in a house shouldn't affect combustion in the equipment, although it could cause spillage from the draft diverter.

You are correct though that it's really foolish for us to recommend solutions on solving equipment problems without examining the equipment. The legal liability if something goes wrong is probably significant.


A got a snippy post from one of the moderators of the board the other day taking me to task for recommending that people have a serice agency make repairs to their equipment. They said this was a board for do it yourselfers, and such advice was not welcome.

Personally I found that comment to be really dumb. Perhaps the MOST important thing for do it yourselfers to know is when they are getting into risky or dangerous kinds of projects. Failing to inform people of such risks is foolish and exposes those giving advice to yet more liability, I would expect.

Anyway, we have some differences in how we answer some questions and issues. That's perfectly fine, in my view, and this kind of discussion helps air the reason for such issues.


Regards,

My main concern in these forums is to SAFELY, explain possibilities that could be causing a problem and what the best way to fix it is, according to my knowledge and experience. I also will tell someone if I think it is not safe for the homeowner to fix it themselves, and if they should call a professional.

Some people just want the info so when the professional arrives, they are sure they are not getting ripped off.

I will clean it this afternoon. I am curious as to how the symptoms I described would indicate that the burner and orafice are dirty.


If the pilot flame is soft with a somewhat yellow appearance: dirty pilot

If the pilot flame is small and blue with a sharp edge around the outside of the flame: orifice is restricted.

Either way chances are the thermocouple is not getting hot enough.

Hello there Mark ---

"Can't" is not a word in my vocabulary as a repairman. However, I am acquainted with a variety of colorful expressions that can come in handy with balky equipment.

I didn't mean to start a war.

I'm not so sure what you guys mean by "soft" or "sharp", but my pilot light is blue. I have another water heater that goes to another section of my house, and both pilot lights look about the same.

Don't worry, be happy.............:):):)

No war, just a little off topic battle :eek:, and all done now.
We are all entitled to our own opinions and mine is the only correct one:rolleyes:.
Just kidding.