You should have one in the compartment that is on the far left edge of the dash, accessible only with the driver's door open, with the little notch that allows you to get a finger or [careful!] a screwdriver in there to pry open the lid. Inside there, you should find a folded copy of the fuse diagram - in German and British English.
Let me know if you find it. If not, I'll see what I can do about getting a copy of our '02 C240 posted, though it is not going to have everything your C320 has.
Drives: P.O.S. silver 2002 C320 sedan w/ every useless option
I looked there already. I'm guessing the dealer used it and never put it back. I called them already about it, and they haven't gotten back to me. If you could get me a copy of yours, it would be a start. Thanks.