I have a 1991 240sx Coupe. The A/C has been working flawlessly for a couple of years now. Last week, the a/c fuse under the dash blew. I replaced it with another 10 amp fuse and it lasted about three days. Today, it blew again and I replaced it with a 15A fuse (All I had in the car ), and it immediately blew again. How do I begin troubleshooting this?