Beginning January 1, 1972, all cars are required to have a warning system which operates a buzzer and a warning light if either the driver's or the right-hand front passenger's seat belts are not fastened when the seats are occupied and the car is in forward motion.
On Chevrolet products, this system consists of seat belt retractor switches, pressure sensitive front seat switches, a parking brake switch (MT), or a transmission switch (AT), a warning light, and a buzzer.
The seat belt warning system is wired through the 20 amp "Gauges" fuse.
The warning light is located in the instrument cluster; and the buzzer, which is shared with the ignition key warning system, is taped to the instrument cluster wiring harness.
The warning system is activated when the ignition switch is ON, the front seats are occupied, and the seat belts are left in their retractors. Only when the front seat belts are extended and properly fastened, will the warning light and buzzer stop.
Two different types of switches are used to control the operation of the system, depending upon the type of transmission used:
On manual transmission-equipped cars, the parking brake warning light switch is used to activate the seat belt warning circuit through a relay as soon as the parking brake is released. A diode is used in the circuit to prevent feedback to the brake warning system.
On automatic transmission equipped models, the seat belt warning system is activated by the neutral safety/back-up lamp switch, when the car is placed into any forward gear and the seat belts are not used.