I tried to install a new Honeywell Programmable Thermostat. When everything was connected the fan for my unit stated running. It has not shut off even when I put the old thermostat back in place. Can anyone help?

Going to need some more info. Does the fan shut off when thermostat wires are disconnected? Try unhooking thermostat wires at control on furnace and see if blower still runs. IF thermostat wires are unhooked at furnace board, and the blower still runs, then you have a problem in furnace, but if blower shuts off when wires are disconnected, then it is a problem in thermostat or thermostat wiring. Please let me know more about this and I will try to help.

Sounds like the circuit board has a blown low-voltage fuse.

Kc13 makes a good point. You may have blown the fuse while wiring the new thermostat. Locate fuse and check. Please let us know if you find it.