how do i open door 1988 mercedes 560sl with no electrical system?

Join the mercedes owners forum

http://forums.mercedesclub.org.uk/index.php

Search on there, or ask in a new thread, and you'll find how to input a live connection through earth points and a live terminal on your car, to provide sufficient energy to operate the door locks.

Quite simple, you just need to know where the connection points are. They are a friendly lot on the forum in the main.

Chicks Fan
August 2010

if you are in aa or rac give them a ring, or call out a car locksmith.

hope it helps
August 2010