Homart (Sears) Gas Forced Air, Pilot Won't Stay Lit. OLD TIMER NEEDED - HVAC - DIY Chatroom Home Improvement Forum

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Old 11-26-2008, 04:23 AM   #1
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Homart (Sears) gas forced air, pilot won't stay lit. OLD TIMER NEEDED

Hello... I am not sure if i need an old timer or not but the gas funace i am having a problem with has to be 40 -50 yrs old (or more) Homart by Sears... It has a standing pilot that has a gas supply which comes directly from a gas cock at the main gas line entering the furnace (not part of the gas valve)... There is also another piece of tubing which does come from the gas valve and appears to be lit by the pilot which then in turn lights the main burner (when heat is called for)... The pilot will go out overnight (also sometimes during the day)... Of course it is very easy to light and never seems to go out while i am watching or while I manually cycle the furnace off and on by using the electric switch at the furnace... I have considered any drafts but this does not seem likely... This is a very basic furnace when it comes to parts etc but is very puzzling... Any ideas on why the pilot would be going out and how to prevent it from happening... Would more info be helpful??? Thank you, John


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Old 11-26-2008, 10:13 AM   #2
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I haven't seen one this old before. You are saying the pilot fuel supply is straight off the gas line? If there is nothing to regulate it, does it keep blowing out gas even with the pilot extinguished? If so then it seems as if it would have to be a draft either from the flue or a crack in the heat exchanger. Hopefully someone with experience with this type setup can help.


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Old 11-26-2008, 10:49 AM   #3
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You either have a thermocouple or power pile pilot safety with a main gas valve separate from pilot system.
The pilot safety may be weak or the pilot orifice is dirty. Could be a crack in the exchanger that blows out the pilot on the burner off cycle as the blower gets close to stopping.

I think that furnace is some what more like 60 years.

That being said I think you should have the furnace checked out before you invest any money into it. It could save you money and your life.
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Old 11-26-2008, 03:49 PM   #4
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A furnace that old would have lousy efficiency. Putting in a new 90+% furnace would pay for itself pretty quick.

Be sure you have CO detectors in the house.
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Old 12-07-2011, 11:48 AM   #5
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Homeart furnace

You probably have the same furnace I have. It was installed in 1950 or so. You can take a very fine sandpaper or emory cloth and "polish" the thermocouple next to the pilot probe. Turn the funace off, shut the gas off for the main supply and the pilot, then wait about three minutes. Clean and polish the area around the thermocouple probe. Then turn the main supply back on, and the pilot supply and press and hold the pressure switch (you probably have already done all of this), light and count slowly to sixty then slowly release the pressure switch. The will prolong the life of the thermocouple, but eventually it will have to be replaced and they are very hard to find. I get mine from the local serviceman, but he operates out of an old, junky shop where he used to maintain appliances before he went to work for the gas company.
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Old 12-07-2011, 09:15 PM   #6
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Someday I'd love to hear the difference tech's get in dcmv closed thermocoupler testing between a dirty pilot and a clean one. A 2 dcmv improvement is all I ever get.
Making sure the pilot orifice is clear & unobstructed however can make a big difference. If the tube that is going from your gas valve to the pilot is 1/8 thick then you probably have a thermocouple which controls the gas valve safety but not the pilot flame.
First, see if you can get the pilot flame to
to enlargen to a harder bluer flame by rapping the pilot assy with a large screwdriver the way you'd knock on a front door. You only need to hit the base assy of the pilot assy a number of times to see if the vibration in concert with the pilot gas pressure will clear any debris. You should do this while the pilot is burning to know when to stop shaking the pilot assy. If the pilot flame does change from a soft flame to a harder flame then wait to see if thats all you need to do.
Many pilots of that age also have an air port in the pilot assy 3 - 4" below the pilot flame that may need to be blown out. I use the plastic feed line of a toilet for that but any small tube thats long enough will do. This applies to pilot assys for both thermocouples and thermopiles.
Anyway.. a photo of the pilot assy will make things easier here.
I still actively service furnaces like yours but I gather that in harder climates they are now a rarity.
The advise of watching the pilot flame through an entire heating cycle to see if a possible exchanger crack is allowing the fan to blow the pilot flame around is a good idea.


Last edited by how; 12-07-2011 at 09:36 PM.
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