Furnace Kicks On and Off and On and...

While working in the garage yesterday, I noticed that my furnace is cycling on and off *constantly*. I hear the gas jets kick on and they burn for about 15 seconds, then shut off. About 30 seconds later it repeats the process, over and over and over again. Only occasionally did the blower kick on where hot air was pushed through the house.
I don't know a dang thing about furnaces, but this can't be normal functioning of the furnace, can it?
-F
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Nope. Not normal. If you know nothing of furnace repairs call a reputable repair company. It could be one of several things, but most likely a bada thermo-couple fo some sort that is causing the burner to shut down before the blower comes on. I'd get it looked into before the really cold weather hits!

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Maybe a flame rectification problem....

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Hmm. If you rectifier, that mean you put it out? (say it slow: Wrecked the fire)
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Boy, you ain't got a clue.
If you were truing to be funny, you missed.

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in message

Here too.
Except it would have been a license....
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typos....typos...
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in message

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Fleemo wrote:

Nope, definitely not normal. Could be a number of things (bad flame sensor among them).
Here is some troubleshooting help -- however, gas isn't something for the untrained DIYer to mess with. I'd recommend you call a professional.
http://toad.net/~jsmeenen/gasvalve.html
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Fleemo wrote:

How about starting with your furnace model? Tony
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Not enough info to even begin to tell you where to look, but as others have suggested, if you are not familiar with the operation and sequence of proper events, call a company, and make sure they are licenced and insured.
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snipped-for-privacy@comcast.net (Fleemo) wrote in

Mine was doing that. It was the thermostat doing it.
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wrote:

There is a long list of possible causes. The least likely of all of these is the thermostat.
Gary R. Lloyd CMS HVACR Troubleshooting Books/Software http://www.techmethod.com
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041121 1403 - Fleemo posted:

In general, there are two limit switches in the furnace plenum: the fan limit, and the gas solenoid high heat limit. It is obvious, in your case, that the fan limit is set too high and the heat in the plenum is rising above this setting to a point that the gas valve high limit is tripping the gas valve closed. When it cools, it turns the gas valve back on again and this cycle repeats. Find the fan limit and set it lower, maybe around 140 degrees and see if that will make a difference. From your description, it is obviously not the room thermostat. If you cannot change the settings on the fan limit switch, maybe it is broken and needs replacing.
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It's an old Payne, model #518A036CC.

suggested, if you are not familiar with the operation and sequence of proper events, call a company, and make sure they are licenced and insured.<
Called several over the past few days. Most have not even bothered to return the phone call, while the others say it'll be the end of next week before they can make a service call.

Anywhere online where I might see a photo or diagram of what the fan limit looks like? I'd rather attempt a simple fix first, and if that doesn't work, wait ten days for a pro.

Yeah, I don't think it's the thermostat, otherwise wouldn't the blower be kicking on and off too? I noticed today that when I turned the thermostat down (from 72 to 68) the cycling stopped. But as soon as I set it back to 72, it started continuously cycling again.
-F
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Looked it up...limited support from Carrier.

Depending on your part of the country, thats normal for this time of year... Also, since the election, this trades business has taken off for the better companies.

and you should, since if you dont know what it looks like, or even if you have one, you can create more damage than you have now. Not all of those old Carrier/Payne units had them. Particularly since the blowers were on timers that were hardwired into the controls.

Depends onthe thermostat you have. While the least likely item would be the stat, its possible you are #10, and 9 out of 10 issues are not the thermostat, perhaps your numbers up. Wait a bit, get the tech to check it.
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041124 0315 - Fleemo posted:

Check this out for starters...
http://toad.net/~jsmeenen/blower.html
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