Electrical / heated seats
 

Hello, I have recently bought a 500SL R129 dated 1999. My electrical and heated seats only works when the left or right door is opened. As soon as I close the 2 doors, the seats do not work any more. Note this is the same for the 2 mirrors. I investigated the electronics boards under the seats: all is clear, no pollution or moisture. Boards are very clean. Any idea for further investigations and fix this issue. Thanks