furnace fans turns off & on

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Old 12-06-02, 12:28 PM
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furnace fans turns off & on

I am a new homeowner, so I'm not sure about any of the technical terms. I have a Coleman Evcon gas furnace that was installed about 7 years ago. I have no idea what type of maintenance was done before purchasing the house last year. But about 2 months ago, the fan switch on the furnace and the attic fan motor were replaced. At this time we oiled the motor and cleaned out the furnace area and filters. The fan switch was replaced because the furnace would run, the fan would turn on, it would run for a bit, then shut off only to have the fan turn back on again a few seconds later. This only happened for a couple of hours one day, but we replaced the switch to be on the safe side. This week when temps plummeted to zero, it did it again for only about 3 hours. After reviewing the posted messages, I realized that I did have a couple of items in front of the vent on the furnace door. Could this have been the problem? Since I have moved the items, I have not had a problem. If that was not the cause, could you give me some other ideas of possible causes?
I would appreciate any ideas.
 
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Old 12-06-02, 12:39 PM
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Buffy72:

You say you had something in front of the vent on the furnace door .
Is this an application that has no return air ducts, like a mobile home?

If the return air only comes through the door of the furnace then yes, stuff in front of the furnace could cause the problem.

The heat could build up in the cabinet, causing the fan to restart.

Also do you notice the air to be fairly cold coming out of the ducts, just before the fan shuts off?
If it is, the fan switch may need a little adjustment.
 
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Old 12-06-02, 12:54 PM
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It is a manufactured home. From what I was told, the only way that the furnace gets the air return is through the vents on the front. I have about a 1-1 1/2 inch gap between the bottom of all of the interior doors and the carpet.
And like I said that it hasn't happened since I moved the things out from in front of the vent. I don't remember if anything was blocking the vent when we first had the problem a couple of months ago and replaced the fan switch. The furnace is in our utility room, so it is entirely possible that there was something in front of it. If the switch needs adjusting, how do we do that?
 
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Old 12-06-02, 03:33 PM
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Buffy72:

I'm not familiar with your particular furnace and assume it has an adjustable fan/limit control.

It should be the control you had replaced.

You would have to be comfortable looking inside the furnace and working around electricity.

The control should have an adjustment scale on it. A good starting point would be about 120 deg F. cutout.

If your not sure about this you should call your service company.
 
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Old 12-06-02, 04:05 PM
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Blockage

It sounds like to me that the return air flow was restricted, be careful of these plastic bags also that you get from the shopping malls. When the fan starts up it can suck a dry cleaning bag or anything light. I had a customer put a small suitcase in front of the door that had a louver in it, when the door shut, it blocked the air flow. This is most likely due to a buildup of heat in the heat exchanger, the fan is ringing out the residual heat in the steel heat exchanger, I think you already fixed the problem though. Some technicians have found that during the heat season we use the fiberglass air filters because some furnaces can't take the restriction of air flow that a pleated air filter may cause, and then use pleats in the spring for cooling.( they remove more dust)
 
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