my megane also does the same the boot sometimes opens if i use the rear wiper or basically use anything that is electrical in the car.
i took the car back to renault years ago they told me that they cant do anything unless it happens when their mechanic is there.
i think the cars have too much electrical equiptment in them which is a shame as they are good to drive its just the bad wiring that really lets them down i wont be buying another renault
colin, January 2011
