I just purchased a 1987 mercedes 560SL. I tried out my antifheft system to see how it worked, but for some reason it is not working. I used the key with the red dot as stated in the manual. Is it possible that a fuse has blown ?

When they start to get flaky, it's common to just disconnect the alarm brain box. I don't know where it is in a 560SL. Probably against the firewall in the passenger footwell. My guess is that the alarm switch in the driver side door handle is bad. It usually means you need a new door handle assembly. Conjecture at this point.

Sixto
95 S420
91 300SE
87 300SDL
83 300SD