so i just bought a 1987 4000cs quattro. but i can't get in to the trunk much to my surprise. the auto locking mechanism is not working. i cant get the doors to lock and unlock when i pull the up and down on the door lock button. i checked the switch down in the door and it has juice so where does it go from there? im waiting for my hayns book to arrive but though maybe some one on here could help.
thanks

 

Im having the same problem... Mine just started this morning

 

so i figured it out. the way the cars work is with a pneumatic pump system. and the pump is located in the trunk. if the trunk is lock go pull out the back seats. ohh yeah roll down a window in case you lock your self in or out. but after the back seat is out disconnected one of the green hoses leading in to the trunk. then take a hand pump and plug the air intake and attach it to the hose. suck on it and you should hear the locks move. and then go in the back and check the connections near your pump. mine had a wire broken. thats what did it for me.