2000 expedition blower won't turn off.-drains battery?

a switchor the the relay to the fan is blown open. take a tester start at the blower and test back wards. If all fails put a kill switch on the battery.as a quick fix. But each time you restart your coputer has to reset it might run rough for 10 miles/min. and u have to fix your clock & raido stations. If you mean the heater fan i think its a purple wire to the fan is hot.