I don't know if your 94 is similar to my 85, but when I lock (or unlock) there is a "whirrrrr" of a vaccuum pump, which might not working in your case? (fuse, broken pump, etc.) and I was able to hear a hissing from where the line was broken.
Perhaps one of the tech.s here can point you in a better direction.
85 300E euro-spec., twin-turbo AMG aero kit
89 300CE AMG aero kit