Alarm goes off when I lock the car
 

Hi, I am new to this, I am a girl and this is my first post so please go easy on me!!:rolleyes:

I have a 2002 ML320 and just recently when I lock the doors the alarm goes off. I dont have any windows or the sunroof open and it doesnt do it all the time, it just does it occasionally.

Any clues?

Hi Kazza and welcome to this forum.
Is the car parked on the streight surface? There is a sensor in it to preventing it to be towed away or stolen without unlocking the doors. If you are parking down or up hill, the alarm could be activated by this level sensor. It could also be one of the door closure sensors, rear hatch not closed all the way or even hood of the engine compartment has a puch plunger style switch for the alarm circuit (when you open the hood it's the white stick all the way in the back by the rake fluid reservoir). One of these components may need little adjustment to make sure these switches are in the closed position.
Good luck,
Bernard