There is a problem with the driver’s door. It does not work at the door. – No sound from the speaker. – Window lifter doesn’t even click-klick. – Central locking is not possible. Passenger door and trunk close perfectly via the passenger door. Driver door has no influence on the rest, does not work together with the other door. My questions: What can I measure or test? have tried to measure the voltage on the speaker. Nothing! What voltage has to be there? Have removed the plug from the (probably) the engine and there are always around the 10V with two thicker wires, even when the ignition is switched off. I activate the window lifter switch when the ignition is switched on. The voltage changes to about 7V. With the right window only click-klick. There is enough to read about that in the forum.