Just another Air Cond question

[nellotare]

Well, I'm a little excited now.. went and had my AC checked out and it just needed R12.. now we'lll look for leaks, but boy oh boy it's nice to have cold air coming out the vents!

Here's my problem: When I'm running the AC and stop at light or sign, I feel an un-natural vibration. (my diesel vibrates a little when stopped, but this is a bigger vibration that I can even feel in the seat) When I cut the AC off, the vibration stops. I took it back to tech that did the work and we checked the belts.. a little worn, but seems fine. On some other threads it has been mentioned that a circuit exists between tachometer and compressor.. it helps save the belt. Does my car have this relationship? What's happening is that the battery is almost dead when I stop the car after running the AC. It seems as if the alternator may not be charging properly. I am taking it to an indie Merz guy on Monday, but wanted to understand something about how all this works so I can appear intelligent when I talk to him.

Any thoughts will be appreciated.