Originally Posted by BMW-M-Mexico
I'm certain you can get a few hp out of a pulley but can't see how that would not affect A/C or anything AT ALL. Has to affect something. Now, the effect may be so minimal that one should not care, but I would let someone else do it and test it first.
He did say it would affect cooling and charging if you run the engine at low revs for extended periods of time, as in stuck in a traffic jam maybe? Cooling and charging are the real issues to look out for.
I wouldn't worry about the A/C. The A/C compressor will not be on all the time unless you are driving around at noon in the middle of the desert. Even if you do that, and the compressor needs to run all the time, it shouldn't damage the compressor or the A/C system. You'll just get a little less cold air in the cabin. And I guess the compressor might not be running at peak efficiency (I must assume it is designed to run at a specific rotational speed which would change with the pulley), which might mean slightly higher fuel consumption, but it would be a rather small difference I would guess. Just a guess though.