A/C blowing fuses.

I have had several mechanics tell me different things on why my a/c keeps blowing fuses. When the truck is in park and idling, it works ok. Sometimes, when I put it in drive, it blows the fuse. Also, sometimes it doesn't blow the fuse when I put it in drive, but when I drive about 1/4 mile, it blows. I tried to put a larger fuse in (20 instead of 10 amp) it still blows. Some mechanics say its the compressor (very expensive) or the a/c clutch, or a wiring short. I don't think the compressor would be the problem because I can sit and idle for hours and it works fine. I also checked through all the wiring and its seems fine. What do you think it may be?