It's a 25 year old Carrier, with an Ecobee thermostat. It's been working fine for the last couple of years. For circulation, the thermostat is set to run the air handler fan for 10 minutes, once an hour if no heat or cooling is called for. The indoor temp was about 74 degrees. The thermostat is set to cool when the temp hits 76 degrees and turn on the heat when it drops to 70 degrees.
Yesterday, the thermostat wasn't calling for heat or cooling but the air handler fan and the outdoor compressor and fan were running. We noticed it was warm in the house and I discovered there was 90 degree air coming our of the duct! If I turned the T-stat down to call for cooling, the duct output air would drop to about 75 degrees, no lower, and the compressor and it's fan were running.