What to do if a Mercedes window won’t go up?

This article will explain the causes of an inoperative power window in a Mercedes Benz passenger car and answer the following questions: what to do if the Mercedes Window won’t go up? How does a power window system work in a Mercedes Benz passenger car? Is it possible to manually close a window that won’t go up?

Mercedes Benz was one of the first automotive car manufacturers to implement the use of electronics to open and close the windows in passenger cars. Power windows in Mercedes Benz cars are available on all the doors in the vehicle and there are also unique features like a one-touch close and open function, anti-pinch function and convenient open and close.

What to do if a Mercedes window won’t go up?

If the power window won’t go up following are a few things to try before taking your car to an authorised workshop for further diagnosis.

  • If a window won’t go up on a Mercedes Benz car, Check the power supply or battery of the vehicle. Start the car and actuate the power window switch again to see if it will go up.
  • Turn off the vehicle and close all the doors, lock and unlock the vehicle with the key fob and cycle the ignition again. If it is an issue with the door control module, turning the ignition on and off will reset it and the window should operate.
  • Check if there is any unwanted object in the path of the window, the window comes up in a path built into the door, if the path is blocked then the window cannot reach the end stop
  • If all the above steps fail, then check the fuse for the power supply of the respective door control unit. The location of the fuse will be in the owner’s manual or in a booklet kept near the vehicle’s interior fuse box.

If the fuse for the power supply is not okay or blown, then there can be a short circuit in the electrical line of the door control module. Therefore, the vehicle needs to be in an authorised workshop to perform further diagnosis.

The power window mechanism in the Mercedes Benz passenger cars is very robust and reliable but there can be malfunctions due to the following problems.

  • Power window motor

The power window motor can become inoperative due to an internal fault or water ingress, if there is an internal malfunction then it will not turn according to the signal from the door control unit. In such cases, the power window motor is replaced to rectify the fault.

  • Power window switch

The power window switch sends a signal to the door control unit, the states of the power window switches in the Mercedes Benz cars are up, down and one-touch Up/down. Based on the signal from the switch the door control unit actuates the power window motor. Therefore, if the switch is damaged or does not register the change in the signal based on the customers’ input the window won’t go up.

  • Window lifter/winder

The window winder or lifter is a mechanism that houses the window and the electric motor. The latest window lifters on the Mercedes Benz passenger cars are built into the door lining while some older models had window lifting mechanisms in the door. The electric motor spins a gear which makes the power window go up and down; faults in the lifting mechanism can therefore cause the window to not go up. The entire window lifter is replaced to rectify this concern as it is not recommended to repair a malfunctioning lifter.

  • Door control unit.

A software error or internal short circuit in the door control module can cause the window to not come up or go down. In such cases, it is recommended to replace the door control from any authorised workshop. After replacing the door control unit it is programmed and various Teach-in processes are performed before the car is delivered to the customer.

How does a power window system work in a Mercedes Benz passenger car?

The Mercedes Benz power window system consists of a door control unit connected to a power window switch and an electric motor. When the driver actuates the power window switch, the door control unit recognises the change in the switch state and sends the power supply to the electric power window motor. The direction of the electric motor depends on the polarity of the signal given but the door control unit. The door control unit is directly connected to the electric motor via a power supply and ground electrical line. 

The door control unit is also connected to the vehicle CAN network, this facilitates functions like convenient opening and closing where a driver needs to continue pressing the unlock or lock switch on the key fob to completely open all the windows or close them.

The latest Mercedes Benz models also have Mercedes Me connect. Mercedes Me connect is used to connect a smartphone with the vehicle and remotely control it via the cellular network. HERMES is short for hardware for enhanced remote mobility and emergency services. Esim is built into the HERMES control unit and it can be paired to customers’ smartphones at the time of buying the vehicle.

Customers can connect up to 10 vehicles on a single smartphone and operate the power window from the smartphone as long as the smartphone is in the network. The electric motor also contains two hall sensors which save the end stop position of the window in the door control unit. If the motor detects obstruction before this position it goes down and does not close. This is designed as an anti-pinch feature in the Mercedes Benz passenger cars. 

Is it possible to manually close the window that won’t go up?

No, it is not possible to manually close the power window if it is stuck in the down position. The complete power window mechanism is hidden behind the door trim, on a few Mercedes Benz models before 2015 there used to be an access hatch for the door control unit but it is not present on the latest models.

If the window lifter and the electric motors are functioning correctly then it is possible to bypass the door control unit in order to close the window temporarily. A 12 V power supply is given directly to the electric motor in order to open or close the window.

Authorised Mercedes Benz workshops also have Xentry star diagnosis tools that can actuate the power window motor and close the window in case the window switch is not working.

Conclusion

Mercedes Benz makes very reliable cars and the power window mechanism does not have any major reliability issues. Mercedes Benz also gives a 5-year standard warranty in some markets and this will cover any cost to fix the power window-related issues. Therefore, do not buy non-genuine or used parts like the door control unit that needs to be calibrated to work with the window lifting mechanism and electric motor.

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