The seatbelt pre-tensioner tightens any slack in the seatbelt system in the first few milliseconds of a collision by using a tiny explosive charge. The charge drives a small piston which will automatically turn the spool which the belt is wrapped around and tighten it. When the full force of the collision impacts on the driver, they are securely held in place by the seatbelt. This will minimise injury and allow for the driver to be in the correct position for the driver’s airbag to inflate properly, thereby receiving maximum protection benefit.
The seatbelt pre-tensioner uses a similar sensor to that of the airbag in detecting a rapid deceleration in the event of a collision or sudden stop and will deploy immediately. After any collision during which the seatbelt pre-tensioner has been activated, the whole unit must be replaced as the explosive charge within the unit will only operate once.
The seatbelt pre-tensioner is located to the right/left at the bottom of the door column and is attached to the chassis of the vehicle with steel anchor plates and bolts.
The seatbelt can be pulled out of the pre-tensioner normally when there is no load placed on it.