Mercedes-Benz 300D Power door locks are not working Inspection at your home or office.

Common reasons for this to happen:

There are three primary components of the power door lock system that can fail, resulting in a useless power door lock:

• Blown fuse: A fuse is a low resistance resistor that creates overcurrent protection. Essentially, the fuse takes a large amount of electrical current, and converts it into a smaller, more manageable amount of current that the door lock actuator can have. It’s not rare for fuses to blow, and when they do, electrical current will stop running to the door lock actuator, rendering the power door lock system useless.

• Dead power door lock switch: The power door lock switch is a relatively simple rocker switch. It reacts to you pressing the lock or unlock button, and sends a simple signal to the actuator. Like light switches, the power door lock switch can die due to frequent use.

• Malfunctioning power door lock actuator: The power door lock actuator is the part of the power door lock system that actually controls the locks. The actuator is a series of gears, with a set of rack and pinion gears at the end. When the actuator gets the signal from the power door lock switch, a small motor turns the gears. The rack and pinion are able to convert the rotational motion of the motor to a vertical motion, which locks and unlocks the doors. Like the power door lock switch, the power door lock actuator can malfunction due to the large amount of use that it gets.