I have a 1995 S-350 diesel that I replaced the fan clutch about a year age in. How can you tell if the fan clutch is working properly? It does not seem like it spins up real fast like a GM product clutch. You cannot hear it as you rev the engine up. You can even stop the fan with your hand(with gloves on of course)and spin it backwards with the engine running.

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1995 S-350
370K + SOLD
1952 220B Cabriolet
39K kilometers + SOLD
1998 E300D
310K +
2012 E350 BlueTec
120K