Re: Hot Air Furnace Runs Continuously
[Re: Stanton]
#3104630
12/22/22 05:29 PM
12/22/22 05:29 PM
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Joined: Apr 2007
Posts: 2,922 Calgary, Alberta Canada
a12rag
master
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master
Joined: Apr 2007
Posts: 2,922
Calgary, Alberta Canada
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There's a sensor on the furnace (I think called a thermocouple) that senses the gas flow. This thing gets a thin coating of dirt or ash on it and it malfunctions so the furnace continuously cycles on and off. It can be remove and cleaned with emery cloth OR replaced inexpensively. It seems to occur every couple or few years. Its a common problem so googling your furnace make and model should show you where it is. There's probably even a Youtube video.
Have you tried changing the batteries in the thermostat? Thermocouple senses the FLAME . . . it generates a small voltage that is used to keep the gas valve open. Yes, the thermocouple does get a coating after years of use . . . and yes, can clean it using emery cloth. However, this sounds more like the thermostat itself . . . If all else fails, call HVAC contractor .... Good luck.
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Re: Hot Air Furnace Runs Continuously
[Re: NITROUSN]
#3104700
12/22/22 09:02 PM
12/22/22 09:02 PM
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Joined: Sep 2003
Posts: 7,833 east side of Ohio
basketcase
master
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master
Joined: Sep 2003
Posts: 7,833
east side of Ohio
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Some thermostats are powered up by a battery. Make sure yours does not have one. If the battery is dead, the thermostat can't signal the furnace, and the furnace won't run.
Dave
1981 Dodge D150 360 auto
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Re: Hot Air Furnace Runs Continuously
[Re: basketcase]
#3104737
12/22/22 10:59 PM
12/22/22 10:59 PM
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Joined: Jan 2003
Posts: 18,425 UPPER MICHIGAN, MARQUETTE COUN...
NITROUSN
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 18,425
UPPER MICHIGAN, MARQUETTE COUN...
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Some thermostats are powered up by a battery. Make sure yours does not have one. If the battery is dead, the thermostat can't signal the furnace, and the furnace won't run. I agree a dead battery should do nothing. However A low battery will do funny things. When the poster said turning it off and on will fool it for a short time. He should at least verify if there is a battery and if so is it good.
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Re: Hot Air Furnace Runs Continuously
[Re: NITROUSN]
#3104744
12/22/22 11:42 PM
12/22/22 11:42 PM
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Joined: Jan 2003
Posts: 10,614 Freeport IL USA
poorboy
I Live Here
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I Live Here
Joined: Jan 2003
Posts: 10,614
Freeport IL USA
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Some thermostats are powered up by a battery. Make sure yours does not have one. If the battery is dead, the thermostat can't signal the furnace, and the furnace won't run. I agree a dead battery should do nothing. However A low battery will do funny things. When the poster said turning it off and on will fool it for a short time. He should at least verify if there is a battery and if so is it good. Yes indeed, a battery low on charge does all kinds of strange things when it comes to home heating. If the thermostat has batteries, replace them and see what happens. If there are no batteries, replace the thermostat. Start with the easy stuff. I have a furnace in my garage. The last couple years, if you bump the temp up more then a couple degrees at a time, the furnace will blow cold air before it reaches the set temp, because it it will trip off a reset on the circuit board. The 1st time it happened, I called the service people. The tech came in, pulled the side panel off, pushed the reset button and watched the furnace cycle through until it shut down on its own, and called it "fixed". I questioned him about it and he told me "As long as it keeps running and makes it to the set temp, after the reset has been pushed, there is nothing that will show up running through the test procedure. I did have him show me where the reset button was. That was a $200 lesson (the cost of the "service call")! It still does that if I kick the thermostat up more then 2 degrees. I can pull the 6 bolts (I'm down to 3 bolts now) that hold the cover on, shut off the power switch, push the reset, and turn on the power to be sure the furnace burner starts up. After the burner starts, I can put the cover back on, and wait to see if it makes it to the set temp before it starts blowing cold air. If it starts blowing cold air, I redo the reset button. If it has a lot of temp to recover, I might have to push the reset button a couple times. The other day we had to work on my son's plow truck and had to have the garage door open. I shut the furnace off through that process but when we got done, the garage was down equal to the outside temp. It took a little over an hour for the furnace to regain those 30 degrees the garage lost. I had to do the reset button 3 time before it got caught up. When it gets to where it shuts off on its own, it good to go. I'm sure something is drawing more power then its suppose to, or the circuit board has a problem, but as long as the reset keeps working, I'm not paying $200 to have them tell me the problem won't show up in the test procedure again.
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