Interior fan stays on without key

I have a 2002 Mitsubishi Lancer, I had to get a replacement engine cause some dumb-@zz at a franchise didnt tighten the drain plug after changing my oil. Now my problem on different occasions when I turned the car off and took out the key the Interior fan would stay on and when I turned the fan off i would come back the next day with my battery drained. Any clues?

its really strange, a machinist can solute this problem. for the more information about new Mitsubishi outlander please visit:

The fan module is connected to a unswitched BAT fuse.
Check owners manual for fan module fuse, or a BAT fuse location.

If BAT fuse you might need to isolate BAT fuses until fan go's off.