motors?
i believe there are no motors. most german made cars from this era use vacuum. the yellow tube is a vacuum line that comes from a unit called "central locking pump" that is located in the rear of the car. It is a vacuum pump that actuates levers in the 3 doors. line may be ruptured if you hear hissing. can you push the lock button down with your finger?.. if not.. the vehicle may "think" your door is open.