where's the short?
 

I posted this in general tech but I sometimes have better luck here. I have a '84 300sd. The battery drains with the key off. A volt meter between the disconnected terminal and the connector reads about 12 volts with the key off. What is a good systematic way to find the problem? Where is a safe free place to download a shop manual for this car, especially electrical schematics? Thanks for your advice.