My project car 1990 300sl has a problem with the trunk. Wasn't able to work on it for a couple of months and the battery went completely dead. Couldn't get into the trunk to charge the battery so I bought a charger that plugs into the cigarette lighter and charged the battery.
The trunk will still not open with or without the key. Any ideas out ther about this problem??

 

well, there is an other possiblity here in Germany, where I am from. My Merc Dealer used to smash the rear light and grap in.
But try it rather not, ask your dealer first if it works :-)