Check the CD wiring diagrams for a while; find amusing here-to-for unknown electric actuator on them; have cardiac arrest; recover; thank God there's no groceries in the trunk. Then turned the alarm on-off a gazillion times (driver's door lock); repeat as neccessary until it "unlevers"; unplug two wire MB plug to lock actuator!!! Took two days of occasional fiddling.
This is on my MB factory alarm system, but I didn't really know about it until the actuator got really tempermental.
I don't know when MB first introduced the alarm system (around 1984 CA ?), but if you are not worried enough about the trunk contents to need a double lock when alarm is armed, I highly recommend disconnecting this actuator (near license plate lights inside trunk lining). Of course, not many of the old factory systems are still connected by now.
If I got really desparate I was going to run a +12v. signal thru the appropriate pin in the alarm harness under the passenger false firewall. If that didn't work 1/2" drill?
The Golden Rule
1984 300SD (bought new, sold it in 1988, bought it back 13 yrs. later)