Thermostat wont turn on furnace

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Old 10-10-04, 01:25 PM
bhrost
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Thermostat wont turn on furnace

A friend asked me for help in getting the furnace started for the first time this season. A deceased elderly relative used to do this, he was unfamiliar with it. The thermostat was turned up to 75 (more than warm enough to fire the burners) and the pilot light was lit - nothing happened. It is a 50 + year old unit converted from coal burning. His relative had been using it last season with no problem. I looked for a switch that might turn the themostat on and off for the season. The only possible switch for this I found was in the on position. I found something which was marked in faded letters as the(manual) gas control valve. I pushed up a lever on this and the burner came on for about 30 seconds and then kicked out. I did this several times with the same result. Opening up this unit I could see a gear wheel engage something and turn around a revolution before the burner would conk out. The thermostat setting had no effect and would not trigger the burners on even for a second. Might the problem be the thermostat, the burner control, or maybe both? Is there some trick for starting this thing we may be missing or does it need repair? Are there other things that need to be checked? What are some likely causes for the failure?Thanks for any help.
 
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Old 10-15-04, 12:17 PM
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Hello: bhrost

By now I hope you got the furnace fixed. Likely or possibily two problems based upon the problem descriptions. Of which I read two potential causes.

Lever you pushed is likely the reset botton to the thermocouple or pilot generator, depending upon which system is used in that furnace. Once reset it allow gas valve to activate. Problem than likely to be the current produce from the pilot generator (PG) was not enough to maintain the system and burners shut down.

Same can apply to T-Couple. Since older furnaces may not shut down the pilot flame only the (ASO) Automatic Shut Off which only shuts off the gas valve which allows gas to flow to the burners. Which means pilot remains on constantly but burners only shut off.

The wheel is likely to be on the fan temp on/off device. This device senses temperature in the firebox and turns fan on when internal firebox temp is reached. If fan does not turn on, to prevent overheating inside the firebox, that same device or another one, will shut off the burners on the high limit safety device. One possible reason why burners came on and than shut off.

Best left to a pro if not already fix or was fixed. Older furnaces can be hazardous and one needs to be handy, knowledgeable and trained with such repairs on funaces to prevent other more serious problems.
 
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Old 10-15-04, 02:40 PM
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You dont say if you have power to the tstat or not. Need to know.

I found something which was marked in faded letters as the(manual) gas control valve. I pushed up a lever on this and the burner came on for about 30 seconds and then kicked out. I did this several times with the same result. Opening up this unit I could see a gear wheel engage something and turn
I think if when you push that lever down you push it over like ,it should stay down and keep the burner on. Sounds like this is in a old hand fire furnace and that was for when the electric went out.

ED
 
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