Hi i'm new to forum but I hope you can help please, my m class 2004 diesel drivers door wont lock with the remote or key, the interior lights don't work on this only so when opened alarm doesn't work, if I use the key the button on the door moves down but won't will not stay down, is there a sensor inside the door which tells the car the door is open or shut, hope somebody can help me thanks Andy.

 

It sounds like your actuator is malfunctioning. I have the same problem that you are describing. I been planning on replacing the actuator but haven't gotten around to it (been like 2 years already). This is a very common problem with that model Mercedes. You can still lock the door by pushing down hard on the lock on the inside then you can unlock by using key on outside.