(Updated on October 17, 2019)
If you get into an accident in any modern car, its seat belt system will keep you secure in your seat so that you don’t get jerked forward or fly out of the windshield. Of course, this can only happen if you are obeying the law and actually wearing your seat belt.
If so, the seat belt system has a component called the “seat belt pretensioner” which keeps the seat belt locked down during an accident. That is why a seat belt does not stretch or have any slack when it is pushed forward quickly.
How a Seat Belt Pretensioner Works
When your vehicle gets into an accident, there is a sudden deceleration that takes place. There are sensors in your vehicle which detect this sudden deceleration. Once they do, the seat belt pretensioner sends a force which moves a concealed piston in your seat belt system.
The piston will then quickly turn a spool, causing the seat belt strap to get wrapped around it. This entire process happens within less than a second. The seat belt strap will basically lose all its slack, making it impossible to move.
Since you are underneath this belt, you stay safely secured in your seat while the impact of the accident occurs.
As you the driver and front passenger stay secured in their seats, the airbag system will deploy its airbags in front of you. The seat belt and airbag systems work together to keep everyone in the front safe.
If you were not wearing your seat belt in an accident, the airbag would not be able to save you. The force of the impact would be so strong that you would jerk forward or fly through the front windshield before the airbag could even completely deploy.
By staying strapped down to your seat, it ensures that your body is positioned directly in front of the airbag so that it can reduce the physical blow as much as possible.
Read also: Airbag Replacement Cost
Seat Belt Pretensioner Replacement Cost
You will need to replace your seat belt pretensioner each time you get into an accident. The seat belt pretensioner is not that expensive, especially if you replace it yourself. It’s one of the few parts of an airbag system where a professional mechanic is not necessary.
The replacement cost of a seat belt pretensioner is around $150 to $200. The cost of the parts is about $50 to $100 while the cost of the labor is about $100 to $125. You may be able to reduce the labor if you can find a cheap enough mechanic in your area or simply enlist the help of a buddy that likes to work on cars.
Alternatively, there are a few shops around the country that specialize in seat belt pretensioner repair. Simply send them the used pretensioner, they will rebuild it, and then ship it back to you. Repairing or rebuilding the unit will save you some money.