A/C Unit or Thermostat?


Old 06-09-15, 06:27 AM
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Join Date: Jun 2015
Location: USA
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A/C Unit or Thermostat?

My husband and I moved into a new home last fall, and have recently turned the air on with the increase in temperature and humidity. Now, we have differing opinions on what temperature to set it at/turn it on, so when I'm home I either shut the unit off and just leave the fan running, or turn the cool setting higher. However Friday afternoon, I noticed when I turned it back on that a little "service outside system," flashed for a few moments, then the unit eventually kicked on.

This happened again over the weekend, and my husband is convinced that our unit is bad and we should contact a repair person immediately. However, I got to thinking this morning, is it possible that our thermostat is bad instead?

For example, the furnace won't work unless the thermostat is set on the "emergency heat" setting, it won't work on the regular "heat." We also put a new filter in right after we moved in, and yet all winter long the screen flashed "filter," to indicate it thought we should replace it (I will admit I have no idea how to let it know we did change it). Sometimes when the fan is running on the "cool" setting, it either won't shut off or turn on, but if the system is set to "off," the fan has no trouble turning on and off.

And it's not as though the air never turns on, my husband just expects an instantaneous start-up and to instantly be bathed in cold air. We also have an open stairwell to our basement, which is easily 10 to 15 degrees cooler than the main level, and since hot air rises... Right now the cool setting is set to 78, it's 74 with the fan running all night, and it feels pretty nice in the house which leads me to believe it may not be all the air conditioner unit's fault.

Any insights would be greatly appreciated. I'm not against having someone come take a look, but if it's as simple as determining if the thermostat is bad, then I'd rather try to trouble-shoot that ourselves and save a little bit on labor (assuming we can figure out what to do, of course!). For a bit of reference, according to the previous owners the unit was replaced with a new unit in 2011, and they own a family business of heating and cooling, so I don't think it would have been installed incorrectly. Not saying that it couldn't have been, but since they have the only local heating and cooling business and everyone uses them, I assume they know what they're doing.
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Old 06-09-15, 07:24 AM
airman.1994's Avatar
Join Date: Dec 2005
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Time to call a service company.
Old 06-09-15, 11:55 AM
Bob14525's Avatar
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I agree with airman. Since you are having other problems with the thermostat (for heating), it's possible that it's not properly wired or is defective. I had a new furnace & humidifier installed ~5 years ago by a local HVAC contractor. That first winter when it got cold, the air in the house was very dry (humidifier wasn't working). I called their service department and a tech came out. He found that the installer had never connected the humidifier controller to the 24VAC. So, these things (miswiring) can happen. Unless you know how the thermostat should be wired, it's best to leave it to a professional.
Old 06-09-15, 02:17 PM
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Join Date: Jun 2015
Location: USA
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Thank you both. It seems to be working currently, but might as well have someone out to look at it now rather than wait until the really hot summer weather!

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