Seat Belt Buckle Switch: Description and Operation

The seat belt switch is a small, normally open, single pole, single throw, plunger actuated, momentary switch. Only one seat belt switch is installed in the vehicle, and it is integral to the driver side front seat belt retractor assembly. The seat belt switch is connected to the vehicle electrical system through a two-wire pigtail wire harness and connector to a dedicated take out and connector of the body wire harness.

The seat belt switch cannot be adjusted or repaired and, if faulty or damaged, the entire driver side seat belt and retractor unit must be replaced.

The seat belt switch is designed to control a path to ground for the seat belt switch sense input of the Electro-Mechanical Instrument Cluster (EMIC). The seat belt switch plunger is actuated by the seat belt webbing wound onto the seat belt retractor spool. When the seat belt tip-half webbing is pulled out of the retractor far enough to engage the seat belt buckle-half, the switch plunger is extended and closes the seat belt switch sense circuit to ground; and, when the seat belt tip-half webbing is wound onto the retractor the switch plunger is depressed, opening the ground path.

The seat belt switch is connected is series between ground and the seat belt switch sense input of the instrument cluster. The seat belt switch receives ground at all times through its pigtail wire connection to the body wire harness from another take out of the body wire harness. An eyelet terminal connector on the body wire harness ground take out is secured under a ground screw to the left lower B-pillar. The seat belt switch may de diagnosed using conventional diagnostic tools and methods.