Furnace won't shut off


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Old 03-31-03, 10:23 AM
vcrtape
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Furnace won't shut off

I have a Kenmore furnace. The furnace comes on at the set temperature, blows warm air, then cycles to just the fan to cool the element, but the fan doesn't shut off. The only way to shut it off is turn the thermostat off. Does this sound like a bad thermostat or something else wrong?
 
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Old 03-31-03, 10:39 AM
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Yes and No

Actually the only control the thermostat usually has over the fan is to force it to run all the time when the fan switch is set to ON. If you have the fan switch set to AUTO, the fan should cycle on temperature with the call for heat. Make sure the fan switch on the thermostat isn't set to ON.

If the fan stops when you turn the thermostat switch to OFF and the fan switch is in AUTO, the problem probably isn't in the thermostat.

Any more detailed help will require your furnace model and fuel type and possible age of the unit (if model is hard to trace). Also we may need to know more about your thermostat. Brand, model, etc.

Help us to help you.

Ken
 
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Old 03-31-03, 12:02 PM
vcrtape
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More Info

The furnace comes on at the set temperature, blows warm air, then cycles to just the fan to cool the element, but the fan doesn't shut off. The only way to shut it off is turn the thermostat off. But this morning it kept running even after i turned it off at the thermostat. I had to go downstairs and flip the switch on the furnance off, I then turned the switch back on and and the thermostat back on and the furnance then stayed off til it cycled back on when needed and this time shut off normally.

It seems to have gotten worse gradually over time as far as how long it runs after the heat stops coming out of registers. One other thing, may be unrelated it sometimes comes on and then goes right back off and stays off like it made a mistake in coming on.

It's a Kenmore gas furnace model # 867.769412
Manufacture # NUGK050MF03
I think it's about 12 years old.

I have a Honeywell Magicstat CT3200A1001 themostat
 
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Old 03-31-03, 02:31 PM
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Usually the fan part of the fan & limit control is to blame. Sometimes it is set too low and sometimes it just sticks. If you know which control it is, take off the cover and see what the pointers are set at. An average setting is 110 deg. for fan off, 140 deg. for fan on and about 180 deg. for limit. You should see the 3 pointers.

If you need a diagram, go to sears.com click on parts and put in your model no. you can get a diagram of your furnace and buy parts right there if you want.
 
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Old 03-31-03, 02:59 PM
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"One other thing, may be unrelated it sometimes comes on and then goes right back off and stays off like it made a mistake in coming on."

If what you mean is the furnace starts up upon a call for heat from the thermostat and then shuts down shortly thereafter, that is most likely due to the cycle rate built into the Honeywell thermostat. I'll bet it does this more often in milder temperatures then when it's really cold out. There is an adjustment screw on the back of the stat for this.

I agree that the fan staying on sounds like the limit control.
 
 

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