I've had a company come out and tell me the ac and furnace are ran from 2 different fans and they recharged the AC unit. However, prior to this the AC was still freezing over the lines. If I have the thermostat set to 80 for the AC it still blows out air so cold and it freezes over the lines and will not shut off until I unplug it from the main outlet. The inside temperature reads to the lowest of 60 degrees even if I have to set to 80 degrees it just will keep running. When I turn the air off from.the thermostat the ac unit itself will still be running outside but not blowing air inside. The furnace is only 4 years old the AC unit however is 23 years old. Not sure about the thermostats age.

  • What kind of thermostat do you have? Is it one of the really old mercury ones?
    – Machavity
    Jun 11 '19 at 0:25
  • It's a Lux Snap action heating/cooling non programmable thermostat. Here's a link for it on home homedepot.com/p/…
    – Shireyd
    Jun 12 '19 at 4:00

If the outdoor unit continues running while the indoor blower is stopped it would indeed start looking like a freezer. If there's been work done recently on the thermostat and related wiring then it could be that a mistake was made which causes the compressor to run continuously. If this problem has developed spontaneously, a likely cause could be that the contactor in the outdoor compressor unit has welded itself closed. That's the equivalent of the power switch being stuck in the on position.

An HVAC contractor or other person comfortable with a volt meter should be able to identify pretty quickly whether the call for cooling is stuck on, or whether it's the contactor itself that has failed. There should be a pair of small-gauge wires going into the compressor unit. If there's a voltage showing between those two wires (about 24 volts ac), or if disconnecting one of them causes the compressor to stop running, then the call for cooling is stuck on -- a thermostat failure or a wiring problem would be likely. If instead there's no significant voltage between the two wires then the contactor is stuck and should be replaced.

  • I have a hvac technician coming out again and will give him this information. Thank you!
    – Shireyd
    Jun 14 '19 at 23:07
  • Hey Greg. Thank you so much for your help. You were exactly right, there was a bad relay on the AC unit itself and the wiring of the thermostat was wrong. Thanks again! Once I figure out how to chose your answer as correc on here I will, lol.
    – Shireyd
    Jun 17 '19 at 16:33
  • When viewing answers to a question you've asked, find a gray check mark to the left of each answer (near the vote up/down arrows). Click that to turn it green and mark a particular answer as accepted.
    – Greg Hill
    Jun 18 '19 at 15:58

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