Low Pressure Cut-Off Switch
WARNING: This page does not describe the selected car, but rather 38 other vehicles, including the 1987 Pontiac Sunbird, 1987 Pontiac Safari, 1987 Pontiac Grand Prix, 1987 Pontiac Grand Am, and 1987 Pontiac Firebird. However, it is still accessible from the selected car via links, so may be relevant.
Compressor protection is offered by a low pressure cut-off switch that opens in response to a low refrigerant charge.