changing to digital bluetooth thermostat, furnace only

You might want to check on the Dometic Bluetooth thermostat. My dealer cancelled an order last winter because it was discontinued. I went with the Micro Air unit since I have both a furnace & AC.

My thermostat only has one sense wire going to a control box mounted in the AC. That box switched both the AC & the furnace. You might need to add the control unit even if you are only going to run just a furnace. Call Hutch Mountain (MicroAir) and ask if they have a solution...