Furnace turns off for 1-2 minutes, blower continues, furnace kicks back on

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Old 02-14-07, 02:48 PM
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Furnace turns off for 1-2 minutes, blower continues, furnace kicks back on

I just noticed this yesterday, but my furnace will be going nice for awhile and then I will hear it kick off, but the blower continues to spin. After a minute or two, the furnace kicks back on and continues on it's merry way. It's occurring every 15-20 minutes right now.

This is a gas furnace with a newer (2 weeks, maybe) air filter.
 
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Old 02-14-07, 04:11 PM
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Best place to start is to determine if the thermostat has reached it's set point and is shutting off. Don't simply go by what you see for temperature readings at the thermstat. You must find out if the voltage is being killed through the thermostat or not. There are connections at the furnace where you can determine this, with a multimeter (voltmeter), right at the moment the flame shuts down.
 
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Old 02-14-07, 05:00 PM
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Ill bet it just started this when it go real cold out side. It reached the tstat set for heat. The blower ran cause the furnace was still warm. Just about the time it should shut off the tstat calls for heat again. Or if you have AC is the coil clean if not the furnace could shuts off on heat limit
 
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Old 02-14-07, 05:10 PM
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It's not close the heat listed on the thermostat. It's actually doing it every 5 minutes or so right now. I'm looking for my multimeter, but of course I cannot find not now :|
 
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Old 02-14-07, 05:26 PM
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If you DO find your tester, be sure to confirm that it works and records voltage and ohms, before simply putting leads on the furnace and going, "Nope...it's dead".
 
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Old 02-14-07, 05:30 PM
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Originally Posted by Ed Imeduc View Post
Ill bet it just started this when it go real cold out side. It reached the tstat set for heat. The blower ran cause the furnace was still warm. Just about the time it should shut off the tstat calls for heat again. Or if you have AC is the coil clean if not the furnace could shuts off on heat limit
About the a/c business: Good point to bring that up. That can escape one's thinking when trying to diagnose HEAT problems. You are absolutely correct...and all these posters who post about limiting furnaces...that if they have the a-coil above the funace and it is clogged with dust because they did not change filters religiously, that would definitely be a place to look.
 
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Old 02-14-07, 05:42 PM
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I have AC and will be pulling the case apart shortly.
 
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Old 02-14-07, 06:11 PM
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Pulled it apart and the coil are clean, shockingly clean, as a matter of fact. However, with the cover off of the coil and the furnace going, I couldn't get it to reproduce the issue.

EDIT: What am I looking for from the thermostat? I have 7 wires, which ones should I be probing?
 
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Old 02-14-07, 06:20 PM
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However, with the cover off of the coil and the furnace going, I couldn't get it to reproduce the issue.
Then that let more air out and you didnt hit limit WHY WHY Is the duct all ok and open????
 
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Old 02-14-07, 06:24 PM
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Originally Posted by Ed Imeduc View Post
Then that let more air out and you didnt hit limit WHY WHY Is the duct all ok and open????
I could only assume so. I'm on a crawl and none of the ducts have ever been closed.

Also, the furnace has been running fine for 20 minutes. The only thing I could assume was I "reset" the thermostat, since that was the first time it was turned off since October
 
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