How to you change an alternator in a 1991 Saab 900s?

To access the alternator, you have to remove the A/C compressor.

First you must remove the alternator belt by removing the adjustment bolt on the alternator. Move the alternator as far down as you can. This will give you access to the lower bolt on the A/C mounting bracket.

Remove the A/C belt. You may have to remove the idler pulley to do this.

Remove the three bolts (probably Allen head) that mount the A/C compressor bracket to the engine and swing the A/C compressor off to the right side of the engine compartment. Do NOT disconnect the A/C hoses.

You should now be able to remove the bolt(s) that hold the alternator in place.

Assembly is reverse of disasssembly.