My honeywell Thermostat reaches the heating temp. but the fan will not stop running.And yes the fan is set to auto.It just keeps running and running and running.It stays the same temp but will not shut off when it reaches the correct temp..

Hello Donna,
You are right. The Auto setting will allow the fan to shut off when the fan is no longer needed.

you need to go into the setup menu and configure your tstat for what type of heating you have.

If you need further help, reach me via phone at https://www.6ya.com/expert/thomas_092728000e6acb79

Do the easy stuff first! Is this a new install or has it been working well for a time and now it is not? Is the entire unit continuing to run or just the fan? Thermostats generally turn the unit on and off when the desired temp is reached but the fan itself (not the compressor or heat strips) typically operates in 3 modes, off, on or auto. check the fan setting.

What temperature is this heat pump being run at? If it is low ambient temp outside this may be running in what is called defrost mode to where the compressor will run without a call for heat. This seems normal to me as long as the setpoint temperature is being reached.

Most T-Stats have a On / Auto on a forced air system. On means the fan will run all the time even if it is not calling for heat. Auto only runs when calling for heat. Does the fan turn off in the auto mode at all? To test it...BE SURE THE FAN IS IN THE AUTO MODE ON THE T-STAT... Turn the thermostat all the way down and keep it there for appox 15 mins. If it is wired properly and the fan limit is set properly the fan should turn off. If it doesn't it is not the thermostat were the problem lies.

Most forced air units have a fan / high limit switch. There is a setting on the switch for the fan to turn on and a setting for the fan to turn off or it has a setting and a differental switch for it to turn off/on. Example - the fan comes on when the temp in the heat exchanger reaches 110 degrees F and will shut down at 95 degrees F after the thermostat is satified...this would hav a differental of 15 degrees F. It may be set to low and the fan continues to run long after all of the heat has been removed from the heat exchanger. This in turn will cause cool air to be coming out of the registers.

Do you have a heat pump? And if so is it a heat pump compatible thermostat.

I have a honeywell TH8320U thermostat and American standard Air handler with heating unit put in. THE thermostat works fine with the ac and follows the programs I have set. However the heat is a different story. The thermo clicks on to follow program but the unit does not run. (auto settings) If I place the thermo in heat and turn it to on I get heat?

Well, here is the deal: unless you rewired from two wire to multiple (usually 4 to 10 wires) wires, the fan cannot be controlled from the thermostat, even though the thermostat indicates that it can > it is a physical wiring and fan administration issue.

Unless you have a newer furnace, the fan is controlled by plenum temp. Works like this: burner turns on, no fan until the plenum temp reaches set temp,....then burner off, and fan keeps running until pelnum temp drops, and often the fan may kick on a few more times as this temp depletes.

Make sure your fan switch on the thermostat is set in the auto position and not set on on.

if fan set in auto position- if set in on it will run constantlly.on your thermostat check this first.