Front seat belt tensioner mechanism (Mercedes-Benz E-Class W124)

Most models are equipped with a front seat belt tensioner system, which is designed to remove slack in the seat belt during a frontal collision. Each front seat belt has its own tensioner system, which is attached to the seat belt inertia drum. The seat belt tensioner mechanism is controlled by the airbag electronic control unit. The seat belt tensioner system is activated in the event of a frontal collision, the magnitude of which exceeds a certain value.

The seat belt tensioner system will not deploy in rear or frontal impacts if the impact magnitude is less than a certain value.

When the belt tensioner system is activated, the fuel in the tensioner cylinder burns, which causes the piston to move upward and eliminate the slack in the seat belt system by fixing the inertia drum with a steel cable attached to the piston. If the tensioner mechanism has been activated, the seat belt will be fixed in place and the unit must be replaced.

To prevent the belt tensioner from triggering when working with the seat belt, remove the ground wire from the battery and disconnect the electrical connector from the tensioner.

Warning! If the seat belt tensioner mechanism has accidentally fallen, it must be replaced, even if there is no mechanical damage to it. Avoid any solvents coming into contact with the seat belt tensioner mechanism.