Grand Am Blowing Fuses

I have a 2003 Grand Am with a power sunroof that is stuck in the vent position. It had a blown 20 amp fuse so I dicided to replace the fuse. I replaced it and as soon as I turned the switch on the fuse blew. I have tested this with 25 and 30 amp fuses and the same thing happens. I used a multimeter on the fuse holder itself and am getting an overload on the 400 V setting. Is there any way I can get a wiring diagram or possibly help in finding and testing the motor and switch? Thank you.

I'm not saying this is your problem but check your cigarette lighter for change, I had a dime fall in mine and I didn't know it... It blew the fuse and my door locks didn't work. It blew like 3 fuses before i noticed it was in there. Hope your problem is as simple as that.

Well, I looked and didn't find any change. Thanks for the advice though. If anyone else has any advice i'd love to hear from you.