Mercedes: trunk, hood latch, electric locks

Question
just got a 88 190E and i can't open the trunk. wondering if there is a pattern w/ the button. or did mercedes make a separate key for the trunk?

Answer
The door key should open the trunk. If the Door lock has been replaced, then It may not fit the trunk.
Try this. Start the vehicle and allow it to run for several minutes. Turn of the radio and accessories. Release the hood latch. Turn off the engine.
Exit the vehicle, using the master key,lock the doors and wait for the electric locks to cycle before removing the key.

Open the hood, remove the battery cables (-) first then (+) clean the terminals and cable ends. Wait 20 minutes and reinstall the cables (+) then (-). Insert the key in the driver door and remembering the correct direction from when you locked the door turn the key in the opposite direction and wait for the locks to cycle.
Try opening the trunk without using the key. Just push the trunk button.  If this does not work, insert the key and turn the lock in the same direction you used to unlock the driver door.
If this does not work, you may have a defective vacuum switch on that lock. I think there is an alternative way to get the trunk latch to open, taking out the rear seat back. I think there may be a cable that you can pull to unlock the latch manually.

You could call the dealer with the VIN number and ask their tech department for details. Or they may allow you to bring the vehicle to there lot and have them use a master key to get the lid open. The may need to craft another key. Non and inexpensive process I might add.
Good LUck
Robert.