a couple days ago, my a/c worked great, now it makes a hissing sound from the center vent area and doesnt cool at all.

could this be a vacuum leak? how would the a/c act if it wasnt getting vacuum?

or am i just out of refridgerant?

thanks

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1991 300 D 2.5 Turbo, 220k
also in the family:
1981 240 D 185k
1991 350 SD 185k
2006 S 500
2005 SLK 350