On my 740 station wagon the back door lock cannot me operated with the key because of too much friction apparently between the plastic cylinder and hole in which it rotates. Maybe some MoS2-spray liquid hit it when I tried to dissolve a sticking screw at the backdoor wiper system. The central locking/unlocking works so that is the way I lock and unlock the backdoor now. The problem was worse during winter in earlier years I recall but now it has become permanent also during the dry and warm season. I have treid to lubricate with a teflon based spray from outside whithout effect. Does anybody have a solution for the problem besides changing the whole lock?
Viktor Weisshäupl, Vienna, Austria