The main suspect would have to be the blower motor relay. If the contacts are arced and pitted, they can stick together and the motor will continue running with the ignition switch turned off, but only if you leave the motor speed switch turned on. That should run the battery down within a few hours. Arced contacts will also make an intermittent connection and the motor will not run at times.
Sunday, December 15th, 2013 AT 12:50 PM