Pilot light will not stay lit

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  #1  
Old 01-16-19, 06:01 AM
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Pilot light will not stay lit

I folks. I have an older Sears Power Miser 12 50 gallon water heater that I cannot get the pilot light to remain lit. I removed the burner and cleaned the thermocouple and also inspected the gas orifice for any obstruction or dirt. I reassembled and the problem still persists. It will remain on for a day or two and then go out once again.

Next, I ordered from Sears Parts Direct and completely new burner assembly with pilot light and thermocouple and installed it. It remained lit for a day or so and, then again this morning was once again out. It lit right back up without an issue but still the problem remains.

I can see a nice steady blue flame from the pilot light flame engulfing the thermocouple completely. The flame is stead and no wavering indicative of a draft. The water heater is installed inside the house on the finished basement level of a three story town home and there are no noticeable drafts in the area. The area around the water heater is clean and the two screens protecting the combustion chamber is clean as well.

I am at a loss about how to proceed from here. I've read that the main control valve could cause the issue but that it's a very rare failure for that part. Any ideas other than just bite the bullet and replace the water heater would be most welcome!

Thanks in advance!

Joe
 
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Old 01-17-19, 11:49 AM
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How is it vented? A blocked vent might cause the pilot to go out.

Check the draw at the draft diverter. Before I quit smoking, I would hold a lit cigarette near it and watch the smoke to see if it's drawn up the flue. Now I light a piece of paper, blow it out and watch the smoke.
 
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Old 01-17-19, 12:31 PM
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Hi Steve. That's a good idea and thanks. I did check it via the piece of paper method and it appears to be drawing okay and, when the burner itself has been ignited, there's quite a pull. I may have an issue with a clogged flame arrestor at the bottom of the tank. Although the pre-filters around the bottom of the tank are clear, the screen underneath the burner assembly may not be.

Thanks again.

Joe
 
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Old 01-17-19, 05:23 PM
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The only other thing that occurs to me is a very under-sized or partially obstructed gas line. Has anything changed, like you bought a new giant Wolf gas range?

Your gas supplier will probably be willing to come out and check.
 
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Old 01-18-19, 04:01 AM
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Hi Steve. Nope, nothing new in the system that would be using any more gas than normal. I still think it may be an air starvation problem leading to excessively high temperatures in the combustion chamber causing the over temp protect to kick in and kick out the pilot light when the burner goes off via the thermostat.

I have an idea on how to conduct an unapproved test to confirm this and I'll post back my finding.
 
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Old 01-18-19, 09:40 AM
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Although the pre-filters around the bottom of the tank are clear, the screen underneath the burner assembly may not be.

I believe most Sears water heaters were made by AO Smith. The issue you describe was pretty common with the earlier FVIR technology AO Smith water heaters.
 
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Old 01-18-19, 10:12 AM
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I suspect you are right. As a test, a short test, I removed the glass window in the piece of metal through which the gas lines and igniter wire go. The water heater works flawlessly and with a much more vigorous flame from the burner itself.

I've ordered a "Tightspot" vacuum brush to do a proper cleaning both above and below the screen and reinstall the glass window after cleaning.

Thanks for the confirmation that I may have found the problem!
 
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Old 01-18-19, 02:31 PM
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When the OP said 'older water heater' I assumed it was pre-FVIR. A quick google reveals the water heaters have been FVIR since 2003. It doesn't seem like that long, but there it is.

At this point almost all water heaters are FVIR, and this is a fairly common problem with them.
 
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Old 02-01-19, 05:47 PM
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Not to hijack this thread, but can the pilot flame size on AO smith GVR 40 100's be adjusted? I see a set screw near the pilot gas port which might uncover a pilot adjustment screw below it?

Ive cleaned the flame arrestor again, but still continued to have the pilot go out after the gas valve was satisfied and shut off.

To me it looks like the pilot flame is so small, the burner blows it out when it shuts off. And this continues even after I replaced the pilot assembly.

Thanks
 
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