blower motor constantly runs

[buckhunter]

I have a GFA, downdraft, Goodman Manufacturing, model# GMP 100-3, serial #951083382S, with a build date of 10/25/95.
As soon as you turn the furnaces power switch on, the blower motor kicks in and will not turn off. Unless you turn off the power switch.
I have installed a new Honeywell, round manual heating and A/C, thermostat. This did not fix the problem.
With the power switch on, blower motor running, you can set the thermostat to heat and the inducer motor will engage and the furnace will fire up. Burner operation appears normal and the furnace will cycle on and off. But the blower motor still runs.
On a visual inspection the red indicator light on the circuit board is on; not blinking. No burnt or frayed wires. But the service panel to the blower compartment is getting hot to the touch and I have never noticed this happening before. Also, with the burner on, the furnace seems to be putting out cold air through the ductwork.
Comments or suggestions are appreciated.
Thank you.

16 May 2006
I have also replaced the limit switch and the capacitor. Blower motor still runs, constantly.
Yesterday, 15 May, the furnace ran fine. No problems with the blower motor. But this morning, the blower motor started to run again. Must be something in the air.