With the thermostat satisfied, the blower shuts off but the condenser keeps running. Contacts disengage only after I disconnect from defrost board. Bad board maybe?

  • Shouldn't it be the other way around? The compressor stops but the fan keeps running for a while to get the last bit of cold air. Did you reverse some wires? – Steve Wellens Mar 12 at 15:14
  • That's my thought. Are the FAN and the COMPRESSOR wires swapped. Don't assume the colors or labels are correct. Compare what's hooked up on the unit with what's hooked up on the thermostat. – jwh20 Mar 12 at 15:15
  • Also be sure that the thermostat is sending the correct signals to the unit. Just because you think it's "satisfied" doesn't mean it's telling the compressor to turn off. – jwh20 Mar 12 at 15:16
  • If a recent change without messing with the wires, I would check the contactor on the outside unit the contacts may have welded closed, this or the signal to the contactor from the thermostat is stuck. a model number of the unit and thermostat would be helpful. – Ed Beal Mar 12 at 15:17
  • Do you have a heat pump or an AC? – Retired Master Electrician Mar 12 at 15:32

You could be right. General controls on a central heating and air would shut down the condenser upon disconnect of the "Y" terminal. You can check to see if there is control voltage to the condenser relay once you have disconnected it. If there is no power to the relay then something like a relay has locked it down and won't release until the cycle is completed.

That would mean there is a good chance it is a bad board OR a bad sensor. Being that I don't know how these part operate and what there normal position is I can't comment on how to test the components.

Hope this helps and good luck

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