Because its exact location can vary slightly depending on the specific model and options, it's best to:
1. Consult a repair manual specific to your 1997 Buick Century: This will have diagrams showing the precise location. A Haynes or Chilton manual would be helpful.
2. Use a wiring diagram: Trace the low-pressure switch wire from the AC control unit to find the switch itself.
Caution: The AC system contains refrigerant under pressure, which can be dangerous if mishandled. If you're not experienced with automotive AC systems, it's recommended to have a qualified mechanic locate and inspect the switch.