Blower fan runs to long

I just bought a used Luxaire high efficency furnace for my garage model number PBNU-LD20N100D. The problem the previous owner said was the blower fan kept coming on every 20 minutes. He had a new circuit board installed for reeson unknown to me. I installed the furnace and noticed the blower starts running 22 seconds after the burners start up which is normal I've read for the honeywell fan limit controls. My biggest complaint is the blower fan won't kick off at the 90 deg. which is what I have the OFF set at. It will continue blowing to 55 deg. or lower. (this temperature I'm reading off the fan limit dial). I bought a new honeywell fan limit switch and still having the same problem. Any help would be greatly appreciated.