steve, i don't think it matters one way or the other but i would put it back on even if your a/c doesn't work.

my a/c didn't work for years and the belt just spun around in "neutral" anyhow, so i couldn't see how taking the belt off would improve anything like performance or mileage.

then i charged the a/c on a flyer just to see what would happen and was a happy guy this past summer!

good luck!

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1984 300D Turbo - 231k....totalled 11/30/07 RIP