Our 740 a/c quit the other day on i95, the windows stopped working and we checked and found a blown fuse. We replaced the fuse but everytime we put on the a/c the fuse blows again. We checked all the fuses and its the same one each time. Also the a/c is very warm. Our mechanic just tightened the a/c belt and after one week we started with this problem. Any suggestions, would be appreciated.

As Oil Eater suggested, check out that wire closely. Typically it runs through a very tight spot between the compressor and the compressor bracket. It may be possible that when he tightened the belt, it got rubbed raw around there somewhere.

But, (here comes the bad news) what commonly happens is that something goes wrong in the compressor clutch and it starts drawing too much current. If you are real resourceful and have the time to mess around with it, you could probably grab another clutch assembly at a wrecking yard and swap it. If your system doesn't leak freon and the compressor is still running fairly quiet, this may be a way to get another year or two out of it. You would have to compare the cost and hassle of going this route versus having a new compressor, dryer, and misc seals replaced and converted to R134. I would probably try the "resourceful" (cheap) fix one time.

Check that the wire leading to the clutch is not shorted or missing insulation. It is very close to the back side of the pulley. I am trying to assimilate anything that may have dealt with tightening the belt. The only thing I can think of is excessive play in the bearing allowing the pully to chafe the ac clutch wire.

Honestly I don't think this is it, but I can't think of anything else that tightening the belt would affect your fuse.

Also, be sure you have the right amperage fuse installed. I only mention this because the PO of my car put a 25A in which worked fine on everything but max ac.