BST Activation

Once activated, the ignitor generates a gas charge which is directed down the internal discharge tube

Fig 1: Identifying BST Activation (1 Of 3)

Courtesy of BMW OF NORTH AMERICA, INC.

This causes the tapered end of the B+ cable contact to dislodge from its seated position and immediately open the circuit.

Fig 2: Identifying BST Activation (2 Of 3)

Courtesy of BMW OF NORTH AMERICA, INC.

The force of the charge continues to push the cable contact away from its seated contact. The spring tabs of the housing are compresses as the contact pushes to the end of its travel.

Fig 3: Identifying BST Activation (3 Of 3)

Courtesy of BMW OF NORTH AMERICA, INC.

When the contact hits the end stop of the housing, it bounces back against the return spring which prevent it from closing the contact with the battery.