Horn / Blower Motor Problems

[Electrify]

I am having problems with my 2000 f250 Diesel. I tried to start my truck this morning but the batteries were dead. I put a battery charger on and the horn starts blasting away when I pulled the horn relay I noticed the heater blower motor was running with the key out of the ignition! Could there be a problem with the ignition switch not shutting off the accessories? Or is there a computer system that runs all of the accessories that is messed up? If anyone out there has any ideas?

Thanks

[Electrify]

Update, I plugged a scanner (SuperChips 1705) in the DLC, the scanner turned on, prompted tune or diagnostics, I selected diagnose and the OBD wouldn't respond! Funny thing is that the truck starts good in the cold weather and runs good down the road.