Started having a problem last week where there tstat would reach temperature with the heater on, then tstat would quickly click twice and blower would keep running. I unplugged the furnace, took the Chronotherm III tstat off the wall, plugged the furnace back in and the blower keeps running. I figured the tstat was shot. Got a new Honeywell Pro4000 tstat, wired it up, plugged the furnace back in, and the blower keeps running. Finally, I realized there is a blinking LED that gives out a code