Gas water heater runs for only one minute

I have an American Water Heater ProLine water heater which is about 22-months old. Yesterday, it stopped working and I noticed that the pilot light was off. So, I lit the pilot according to the instructions on the tank and turned the heater ON. The burner came on and I left home thinking my problem was solved. This morning, there was no hot water again and I went through the same sequence and this time, I stayed around to notice that the heater is turning itself off (including the pilot light) in approximately one minute. A few other observations:
- If I leave the gas control knob in Pilot, the pilot light stays on for ever. I checked after 3 hrs and it was still on. I think this means that the thermocouple is NOT the problem.
- If I turn the gas control knob to ON and leave the thermostat on VACATION, the burner never turns on and the pilot light stays on for ever.
- If I turn gas control knob to ON and turn the thermostat hotter until the burner turns on, the burner runs for about a minute and turns off. At this point, the pilot light is also off. I noticed that sometimes the flame turns yellow for a moment or two, especially before the burner turns off, but mostly the flame is blue and looks normal.
I would appreciate any comments or suggestions on what the problem could be. Tomorrow in the daylight, I am going to open the inside door and take a look, but any suggestions on what I should look for would be welcome. I am proceeding under the assumption that replacing the thermocouple will not solve my problem because the pilot light is not going out by itself. Is this thinking correct?
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On 6/10/06 8:48 PM, in article snipped-for-privacy@i40g2000cwc.googlegroups.com, " snipped-for-privacy@charter.net"

Contrary to your conclusion, I think that the thermocouple IS the problem.
The main valve solenoid draws a relatively large load that the thermocouple is not able to supply--at least for long. The result is that both pilot and main valve drop out. Maybe the holding valve for the pilot light is on the borderline. In that case, it may shut off the pilot light when the main solenoid turns on.
Unfortunately, it is usually difficult to get to the thermocouple terminals to measure this voltage. It is probably much easier to replace the thermocouple than to troubleshoot it. If you have an inquiring mind, you can test your new thermocouple on your gas range under various loadings. When the old one becomes available, you could do the same with it and compare.
I should point out that I have run into similar problems in the past, but by no stretch of the imagination am I a pro at this.
Bill -- Ferme le Bush
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Salmon Egg wrote:

Salmon, Thanks for your response.
I am afraid I am not expert enough to understand this explanation. Isn't the fact that the pilot light stays on for ever (so long as the burner doesn't turn on) an indication that the thermocouple is OK?
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On 6/11/06 7:21 AM, in article snipped-for-privacy@h76g2000cwa.googlegroups.com, "tinkynan"

It would have been more interesting if you actually found out what the problem is.
The thermocouple has to operate both the pilot and the main valve. It may not be up to it and then one drops out.
I once had a problem with a gas range. It turned out that oven solenoid had magnet wire with poor varnish insulation. It was exposed to natural gas. Natural gas really attacks copper. The wire was reduced to a thread. I found the problem when I was trying to get a Thanksgiving turkey going. I ended up putting a dry cell in series with thermocouple. That combination gave me what was needed to finish cooking.
Bill -- Ferme le Bush
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snipped-for-privacy@charter.net wrote:

Once the thermocouple energizes the solenoid inside the gas control, both pilot AND main burner gas passages are opened and stay open.
I agree; this is not a thermocouple issue.
QUOTE: "I noticed that sometimes the flame turns yellow for a moment or two, especially before the burner turns off,"
This may be the pertinent clue. This is an indication of insufficient combustion air. Since this is an atmospheric burner, draft is produced by the flue. If the flue is blocked, air supply will be cut down. 22 months seems like a short life to have developed an internal flue problem (buckled tank inner flue passage) but it could happen. Chimney flue could be blocked too.
That's where I would begin.
Less likely, I think, is a restriction in the gas supply which causes the gas pressure to drop off when the main burner comes on. But look into both.
Jim
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Speedy Jim wrote:

Jim, Thanks a lot for your response. I think you may have put your finger on the cause of my problem.
This morning, I have been trying to open the water heater inside door and guess what I heard. Beautiful bird chirpings from inside the flue! I ran out immediately and looked at the chimney flue on the roof but didn't notice any birds (probably flew away). Couldn't see any nest material sticking out but from my viewing angle on the ground (this is a 2-story house), it would be hard to see.
For the few moments I heard the birds, they were really loud so I think they were real close to the flue if not right inside it. My current best theory is that the birds blocked chimney flue with their nest (probably built over the last couple of days) and the burner is shutting off after consuming the little oxygen there is in the passage from the tank to the roof.
Now, I am at a loss as to who to call. Not the plumber, right?
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Chimney sweep is the one to call, get a stainless cover for your flue/s so this doesnt reoccur...
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Here is an update.
I called a plumber finally and he didn't believe in my theory. He replaced the thermostat and the burner in turn and that didn't solve the problem as I expected. He totally discounted my theory about birds blocking the flue because he says it is too hot for birds to build a nest. Eventually, he came up with his own theory that there is a small leak in the tank and that falling water drops were putting out the flame. He called the heater company and convinced them of his diagnosis and got them to replace the heater under warranty. I now have a new water heater and had to pay $400 for labor. I am quite sure I was overcharged for labor and my wife thinks I am stupid. Anyway, the new water heater appears to work fine.
End of chapter.
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wrote:

If you have bird chirpings from inside the flue, I think you have the bird flue. AFAIK, this is the first case in the United States.

If they flew away, it means it could be spreading. Please contact public health authorities immediately.

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