# Williams wall furnace pilot won't stay lit



## TarheelTerp (Jan 6, 2009)

Mark1957 said:


> My williams model 3509622 wall furnace pilot won't stay lit.
> I replaced the pilot generator, cleaned the pilot orifice...


won't STAY lit or won't light at all?



> If that doe'nt do it, maybe the gas valve went south.


How old is it? 
How long has it been since the equipment worked right/well?


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## how (Feb 26, 2011)

I don't think you can bypass the generator as it supplies the voltage that runs the gas valve. To diagnose a problem you can bypass the other electrical loops to the safety controls that may share a common connection with the generator at the gas valve.

Does the pilot flame fully envelope the pilot generator? Does the pilot have an air mixing port at it's base that might be filled with dust? Are all the electrical connections completely tight (1/2 V systems only require a small amount or resistance to stop a gas valve.) 

Do you have a meter that measures dcmv?


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## Mark1957 (Dec 31, 2011)

I think I found my problem. The pilot burner is split down to the base. It will light and burn, but when I release the pilot button, it sucks air and extinguishes the flame. I didn't notice this at first and have gotten away from heating systems at work, and didn't feel like tearing apart my only other wall heater to double check. We had a problem at work with a water heater that had a split in the gas feed tube to the pilot, only it would blow out when the main burner shut down. I let you know if I was right, but the parts store is closed tomorrow.


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## how (Feb 26, 2011)

Quote
It will light and burn, but when I release the pilot button, it sucks air and extinguishes the flame. 

I think your diagnostic conclussion is wrong or I am not understanding what you are saying!. Pictures would help.

If when you press in the pilot button, the gas comes out of the pilot and envelopes the power pile(generator), what changes with the releasing of that pilot button that then allows the air to be sucked in to extinquish the flame?
The same conditions exist with the button in and the button off, except that the button manually allows the gas to flow out the pilot tube, whereas when the pilot solinoid in your gas valve is engaged it only holds open what the button was manually doing.

A split in a pilot tube line of a hot water tank would make for a very soft pilot flame that would be susceptible to pilot outage for different reasons.
Metering the dcV output of the power generator will give you a basis for figuring out what's wrong and some pictures will help us participate.


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## Mark1957 (Dec 31, 2011)

I replaced the main valve and that was the problem. I replaced the original with a Robertshaw series 700-502. Rewiring is a bit trickier because you have 3 terminals instead of 4. You hook up as indicated, but the single thermostat on the spade connection has to instead be wire nutted to the high limit and the other high limit end goes to this connection, so if your high limit goes out, your thermo:thumbsup:stat can no longer call for heat.


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## how (Feb 26, 2011)

Good to hear you've fixed it. I checked on line to see what valve you choose and saw $97.00 on the first site and $239.00 on the second. Obviously pays to shop around.


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## Mark1957 (Dec 31, 2011)

Johnston, through a friend who has an account. $52.00. $58.00 with tax. Had to rework the pilot line. Total cost of repair with a new pilot assembly about $120. Good learning experiance. I had a small gas leak around the pilot line. Shut down unit and brought home a gas leak detector from work. Turned on gas checked with detector around main shut off , flex line to control valve-ok, sprayed fittings with gas leak solution, -ok. Relit pilot and sprayed around pilot connections and tightened one about 1/4 turn were bubbles appeared. Up and running.
:thumbup:


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