What kind of coolant is in the air conditioner on a 1991 Buick Riviera - Freon or 134a coolant?

The 1991 Buick Riviera originally used R-12 refrigerant, commonly known as Freon. However, due to environmental regulations, many vehicles from that era have been retrofitted to use R-134a refrigerant instead. If the air conditioning system in your Riviera has not been modified, it will still contain R-12. It's essential to check the system to determine which refrigerant is currently being used.