Furnace Won't Shut Off with A/C


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Old 07-07-13, 03:19 PM
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Furnace Won't Shut Off with A/C

Had the thermostat set to 80 while away for weekend. Came back and temp in house was 70. Outside unit was running, but little snowflake on thermostat was not on. Turned thermostat off and the outside unit shut off. However, the furnace was still blowing air through the vents. Normally it shuts off a few minutes after the outside unit turns off, but a half hour later and it was still running. I tried flipping the breaker in the fuse box, but when I turned that fuse back on, the furnace started blowing air again, even though the thermostat is set to off.

I tried turning the heat on (and it blows heat). The outside unit turns on and off with the thermostat, but the furnace continues to blow air regardless. It is now blowing warm air.

Why would the furnace refuse to stop blowing air if the thermostat is off?
 
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Old 07-07-13, 03:26 PM
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Welcome to the forums.

The outside unit is not always shutting off with the thermostat if you came home and found 70d air with the thermostat set for 80d.

I'm guessing you don't have the switch in FAN ON mode at the thermostat.

We're going to need a make and model number of your furnace/air handler and at least a make of your thermostat for a start.
 
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Old 07-07-13, 03:42 PM
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Thank you for your quick response! As I was just standing and staring at the furnace, it finally shut off. I pulled out the filter to see how dirty it was, and it was pretty dirty (though I just changed it not so long ago). Could a dirty filter make the unit run nonstop?

The furnace and outside unit are both Payne. The indoor unit is model #FB4CNF024 and the outside unit is model #PH13NA024-B. They are approximately 2.5 years old.

The thermostat is Honeywell, and I don't think they replaced it when they replaced the indoor/outdoor units. The fan is set to auto, not on. I've never touched that button.
 
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Old 07-07-13, 04:22 PM
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I see lots of posts where people immediately blame the thermostat and after they replace it the problem remains. Here, I think a faulty thermostat is a definite possibility. A model number of the thermostat would help.
 
 

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