light problems

I have a 84 fiero parking lights and dash lights not working. I changed the fuse and when switch is turned on it blows the fuse. If you leave the switch on then put in a fuse everything works but when switch is shut off it blows the fuse. so I replaced the switch with a brand new one. and I still have the same problem. can anyone help me? thanks

There may be a positive wire rubbing against something metal, and the insulation has rubbed through. Based on what you've told me (the problem can happen turning the switch both on OR off) the bad spot is probably between the fuse box and the switch.

Have you checked the isolation realy for the headlight motors? Common problem.