My AC compressor recently started running whenever the heat kicks on. It is not a heat pump. The compressor is a Nordyne fs3ba-036ka. I haven't done anything to the system aside from changing filters since last winter, so I've no idea why this would just start happening. Any suggestions are appreciated.

  • It sounds like your thermostat has a problem. If the cooling system is turning on you can pull the RC wire and that should stop it for now. But something is wrong with the thermostat output. By removing the RC output the compressor should not start. – Ed Beal Jan 1 at 7:43
  • What make and model is the furnace? Do you have a multimeter to troubleshoot this with? – ThreePhaseEel Jan 1 at 12:29
  • Thermostat has an issue, or some wires got pinched/cut/whatever when you were messing with the filter (assuming filter is in the air handler). – JPhi1618 Jan 2 at 16:33

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