Impact Sensor: Description and Operation

The sensor assembly is a switch which reacts to impacts according to direction and force. It discriminates between impacts that require air bag inflation and those which do not. When an impact occurs that requires air bag inflation, the sensor contacts close, completing the electrical circuit necessary for system operation.

The crash sensor is constructed of a ball in a tube with contacts at one end.

The ball is held away from the contacts by a magnet at the opposite end of the tube. During an impact, if the change in vehicle's velocity is great enough, the ball will break away from the magnetic attraction and travel down the tube and close the contacts.

The travel of the ball in the tube is air damped by having a very small gap between the ball and the tube. This prevents closure of the contacts during short duration velocity changes. The major difference between a crash sensor and a safing sensor is the ball to contact distance which is reduced in the safing sensor.

There are five sensors located in the vehicle:
- At the LH tow bracket.
- At the RH tow bracket.
- A dual sensor at the radiator support.
- Under the console behind the hand brake lever (safing sensor).
At least two sensors, one safing, and one front crash sensor, must be activated to inflate the air bag.