Originally Posted by Glasuan
I was told that this was normail too, but it does not seem like a normal thing for a car. Especially because it is in off, and I can adjust the temp control. The fact that it is on, means that I am losing a percentage of my HP.
Um, not really, no. If the _compressor_ is running, that could exert a really slight parasitic drag, but the car cuts it out under hard acceleration, plus you can always just leave the A/C switched off under those circumstances if you want. (If you have the C62 electronic A/C, just press the Econ manual button and get out of Auto mode.)
The vacuum system wouldn't affect the engine in normal operation, although if it was actually leaking big-time, that would be something else. (Some vacuum-operated parts such as certain EGR valves, like on the Buick/Olds 3.8L V6, are _designed_ to leak vacuum, so they won't operate at all unless they're on a steady vacuum draw.) Keep in mind also that when you want to turn off a vacuum-operated component, you actually have to do it by letting air _in_ somehow, so a _controlled_ leak in parts of the system is needed from time to time.