Cut and pasted from another response I wrote on how to replace the alternator:

4) There are three bolts that hold the alternator on, all are 17 mm. Loosen all three (toward the rear of the car), then back the 13mm adjusting nut all the way out.

The one on the bottom (goes through a flange on the engine), can be cracked with an open end or box end wrench, and removed with a deep socket.

The inboard one on top is tough to reach. The bolt head is toward the rear of the car and the bolt goes through a flange on the engine block and is threaded into a nut welded to the alternator bracket. Crack the bolt with an open end or box end wrench and then back it out with a short socket, one ratchet click at a time.

The outboard one on the top only needs to be loosened with an open end or box end wrench at the nut towards the back of the car. The head of that bolt should have a long threaded stud coming of the side going to the 13mm adjusting nut.

5) Once you've loosened the two 17mm bolts and one nut, you can back the 13mm adjusting nut all the way out and slip the belts off the pulley.