AC/Furnace Blower Turning on and off by itself... need some help!!


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Old 09-21-11, 06:35 PM
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Exclamation AC/Furnace Blower Turning on and off by itself... need some help!!

Hi..

Recently I have noticed that my blower from my furnace has been turning on and off randomly. It is the time of year here in Mich where I have the AC on but it is set three degrees higher than the house temp. So we will be sitting and all of the sudden the blower in the basement will come on for as much as 30 seconds to as little as a couple seconds and then go off. The AC condenser outside is not coming on when this happens it strictly is the blower.

I had someone come out last year to check out the issue and was told that it was due to possibly having a bad relay in my thermostat and I should replace it. So I did replace thermostat last year with a newer version than what I had. Honeywell progrmable.. middle of the road type product.

Furnace is 6 years old and is a kenmore
AC is 2 years old and is a carrier. Did not ever notice this happening until the new AC was installed.

When the AC turns on as it should because room temp has triggered it, everything is fine.. cools great.
Same deal when it is furnace time, it heats the house fine.

So I am no expert by any means but I am thinking that this is some sort of wiring issue perhaps? Clearly something is triggering that blower to start up. It has gotten to where it happens several times an hour it used to only happen every once in a while and was not very noticable... now its very noticeable.

Does anyone out there have any ideas. Again I have read things that say anything from a bad relay switch, to bad wires/wiring with the thermostat, to the thermostat itself.

Hopefully I was clear enough with this explination. It is happening as we speak. Have had Tstat on cool, heat, or even off and the blower will still start up. Any feedback would be awesome and if there are questions that need to be clarified let me know.

Thx
 
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Old 09-21-11, 09:41 PM
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Is this an upflow furnace application, any signs of water in the furnace safety switch area?

An open limit switch can energize the indoor fan. A loose or corroded terminal to a limit switch can open the circuit to a limit switch.
 
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Old 09-22-11, 05:37 AM
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Hi again..

I do not know what determines If it is an upflow or not.
There has been water that has trickled under the base of the unit before due to a small trickle I get down there when it rains a lot.
I have been thinking about corroded wire/terminal as a possibility but do you have any idea as to where to locate this if I were to trouble shoot. I can send pictures if needed. Also it should be known that it is dry down there now.
 
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Old 09-22-11, 12:37 PM
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If your T-stat is not calling for A/C, but the blower is on, it is a bad control board which is right next to your blower.
 
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Old 09-22-11, 02:15 PM
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Has not happened all day today I have been home. Only thing different today is now I have the furnace on as it is cold here today.

So when it does happen, it seems that it is when the tsat is set to AC and the temp it is set to is higher than the house temp so it should not start up. And it (the condender outside) does not start. What will happen is I will hear blower/fan start for a few seconds and then stop. The TSTAT is not actually calling for the AC to come on it is sitting idle. AS I said in first post this will happen sometimes if the unit is off altogether.
 
 

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