Front Seat Belt Tensioner Mechanism — Basic Information (BMW 3 Series E46)

1. Most models covered by this manual are equipped with a front seat belt tensioner system. The system is designed to instantly remove slack in the belt during a frontal collision to reduce the possibility of injury to front seat occupants. Each front seat has its own belt tensioner. The tensioner is directly connected to the seat belt retractor.

2. The tensioner is activated when the frontal impact force exceeds a preset value. The system does not react to smaller forces or to rear impacts,

3. When the system is triggered, a coil spring is compressed inside the tensioner mechanism and locks the seat belt via a cable drive. This prevents the seat belt from stretching and does not allow the front seat passengers to move. After the mechanism is triggered, the seat belts remain locked and the mechanism must be replaced to unlock them.

4. When working inside a vehicle, there is always a risk of the system being triggered. To prevent an accident due to the system being triggered unexpectedly, always disconnect the negative battery cable (see chapter 5A) and wait at least 5 seconds before continuing.

5. Before servicing the front seat belts, read the following warnings carefully.

Caution: If the tensioning mechanism has been triggered, it must be replaced, even if the triggering was accidental.

• Do not allow solvents to enter the tensioning mechanism.
• Protect the power tool from impacts, as this may cause the belt tensioner to operate.
• Check for deformation of the outer parts of the tensioning mechanism and brackets. Replace faulty parts.

The text is based on materials from the website: «www.bmwman.ru»