Maybe you could help me?

I cannot ask a question on the forum and I cannot get it to let me register as well.

I have a 10yr old Armstrong Ultra SX 80 furnace. The furnace will receive a call for heat from the termostat it will cycle correctly ( induced draft motor, pilot will lite, gas valve opens I get light off and a full heat cycle but the blower will run continuously once the burners turn off. This will not allow the furnace to enter another heat cycle regardless of the thermostat setting. The only way to reset the system is to turn the power off at the 110 switch and reset the board. Is the problem a bad blower limit, gas valve or a bad board. Is there any way to trouble shoot this without replacing the valve or the board first. The valve is almost 300.00 and the board is 265.00 so it is very expensive. Also is this a common problem?

How about posting the real model number so I can try to look the furnace up. Armstrong has used many different setups on there units so I need to try and find the correct one.