A couple of years ago, I replaced our old mercury style thermostat with a digital one. It worked fine for a while. Maybe a year later, we noticed that the heat would kick on and off fine, however, the fan blows constantly (usually blowing unheated air). The only way to turn off the blowing is through the main fuse panel. The furnace is a Lennox G12-55 model and the thermostat is a RiteTemp 8022. I am worrying about this as the winter months are coming up and the new baby is in the house.
Thanks in advance!

A couple of years ago, I replaced our old mercury style thermostat with a digital one. It worked fine for a while. Maybe a year later, we noticed that the heat would kick on and off fine, however, the fan blows constantly (usually blowing unheated air). The only way to turn off the blowing is through the main fuse panel. The furnace is a Lennox G12-55 model and the thermostat is a RiteTemp 8022. I am worrying about this as the winter months are coming up and the new baby is in the house.
Thanks in advance!
Have you checked on the thermostat to see if there is an ON/OFF/AUTO switch for the air handler part? I sometimes will leave the fan on just to recirculate the air in the ON position. In the AUTO, it will come on and off. Maybe that part of your thermostat isn't working. I'm no expert... just a thought! :)

There is a fan on / auto switch. It acts the same whichever setting it is on.

Likely the fan relay has stuck. Trouble is, it may be on a circuit board, hard to check out and replace short of a very expensive new board. You could luck in and have a dirty or bad limit switch or temperature sensor.