Heater Fan Switch Shorting....?????

[SWINGSAX68]

OK so I'm leaving from the Music Bldg. to go home and sleep, warming up my truck and my fan is blowing cool air at me, no prob shut it off until its warm then switch it back on for heat BRRRRRRRRRRR....when I shut it off I see a flash....blown fuse....so i get in there and replace the Air Con fuse which was busted.....I get back to my place and for sh!ts and giggles I start switching the fan off and on...just to check it out, make sure everything is fine and dandy. One time towards full blast and my dash lights blink off and on quickly....then back to off and another flash of my dash lights....last time to on position and fuse blows again. What happened?????
How can I find this short. I checked my wires, it seems that a larger grey wire comes from the wireing harness to a plug for the switch juice (the grey wire may just be painted on from painting my dash a long time ago grey) Also there is a smaller grey wire that goes to the light for the DEF-FAN-HEAT indicator. I assumed it was for this so I hooked it up as such. Why is this affecting my dash lights. ALSO.......the plug end from the fan switch plugs into the heater box into what seems like a little plastic support with two bolts on either side to mount it on the box.....mine is broken and the plug is loose, could this be my short, jiggleing around and making contact with the box???? Also if I am correct this plug has a small coil at the end, what does this little coil do????
Thanks guys I hope I described everything correctly and I hope you can help me out.....this really annoys me cause I just got my new heater core and my heater was working nicely until now.
-Roger