Puzzling Gas Furnace Behavior


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Old 02-13-07, 01:40 PM
K
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Puzzling Gas Furnace Behavior

I am hoping someone has an idea what could be going on here. The truth is that my gas forced air furnace is working, but exhibits puzzling behavior every other heating cycle. It is a circa 1992 Rheem natural gas furnace with a pilot flame. It is heating fine, but in the last week or two, every other cycle, it fires up, the blower comes on, and then it shuts down within seconds. I've noticed that when it does this, it is already up to set temperature. The thermostat is a digital model, could that be the problem? I've disassembled the flame sensor (??) and cleaned it with steel wool. The pilot flame is mostly blue, but I do notice a bit of yellow. I don't know if this is recent or not. Could it be the placement of the flame sensor in relation to the flame? The tip is about 1/2 inch above the flame. Should it be directly in the flame instead?
I have a gas water heater that is working just fine, so I doubt there's a problem with the gas pressure. I am just worried that this could be a symptom of an impending issue. Anything else I forgot to mention that would help? Oh and, I don't know if this is relevant or not, we replaced the gas valve about 12 months ago. It has worked fine since until now.
 
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Old 02-13-07, 04:44 PM
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What kind of temperature is coming out of a nearby heat register at the time the set temp has been reached and the blower shuts off right away?
 
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Old 02-14-07, 05:12 AM
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Dave,
Not sure what you are asking. Do you mean I should put a thermometer in a register and measure the temp? I doubt it will get a chance to heat up much before it shuts down. Or do you mean is it blowing cold air? It isn't.
 
 

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