I have a 2006 Gmc Sierra and about 2 weeks ago the AC started blowing really hot air. I started with checking the freon charge which was good, so i ensured that the compressor was working, which its was, so i then checked that all the fuses were good and they were so i ended up changing the main AC control unit and it fixed the problem for about 3 days, but then the exact same thing started to happen! What would be causing that board to short without blowing a fuse?