Fan Won't Shut Off Automatically: Troubleshooting a Heat Pump and Thermostat (2023 Update)

I know his may be an age old problem but I can't find a post describing my exact problem. equipment - New Lennox Heat Pump unit. Thermostat - White Rodgers heat pump thermostat (6 months old)

Problem example: Set point set at 69 degrees. Unit will come on normally with fan on, heat strips on and heat pump compressor energizes.

When inside heat reaches 69 degrees, thermostat clicks and heat strips turn off and outside compressor de-energizes but,,,,, fan continues to run and will run all night if temp stay at 69 . If temp falls below 69 set point, heat strips will again come on and compressor with energize again. Cycle will continue with the same result,,,,, fan will not shut off.

** If I manually raise the temperature myself to 70 degrees, the fan will turn off. *** Process will repeat itself no matter what temp I set it at.

Fan is in Auto setting, Control is in Heat setting, not emergency setting.

You guys have any idea what my problem might be? I would suspect the thermostat but I had the same problem with the previously installed unit and another thermostat. Bad wiring / shorting out? If wiring were shorted, fan wouldn't shut off when I raise the temp manually.

I tried changing the batteries in thermostat as one guy suggested. Put in new thermostat? I could try that again, but hate to go through the expense and I have two of the same thermostats (upstairs and downstairs). Have to teach spouse to use yet another thermostat. Not what I really want to do!

ANY ideas would be helpful! Thanks!

It can be frustrating when your fan won't shut off automatically, even when your set temperature has been reached. Based on the information you've provided, there are a few potential causes of this issue.

Thermostat Wiring: As you've mentioned, bad wiring or shorting out can cause the fan to continue running. Make sure the wiring connections between the thermostat and heat pump are secure and free from damage.
Faulty Thermostat: While you've already replaced the thermostat once, it's possible that the replacement unit is also faulty. If you haven't already, try resetting the thermostat to its default settings and see if that resolves the issue. You may also want to try a different brand or model of thermostat to see if that makes a difference.
Heat Pump Sensor: Another potential cause of the fan not shutting off could be a faulty sensor on the heat pump. If the sensor is not reading the correct temperature, it may continue to run the fan even when the desired temperature has been reached. Contact a professional HVAC technician to inspect and test the heat pump sensor.
Fan Relay: A faulty fan relay can also cause the fan to stay on, even when the thermostat is not calling for heat. Again, a professional technician can diagnose and repair this issue.

In summary, if your fan won't shut off automatically, there are a few possible causes to consider. Check the thermostat wiring, try resetting the thermostat to its default settings, and consider the heat pump sensor or fan relay as potential issues. If you're not comfortable troubleshooting these issues on your own, it's always best to contact a professional HVAC technician for diagnosis and repair.