A 1995 Chevy C20 van likely used
R-12 (Freon-12). However, it's
crucial to verify this. R-12 was phased out due to its ozone-depleting properties, and many vehicles of that era have had their refrigerant systems converted to use R-134a or other refrigerants.
You should not attempt to determine this yourself. Have a qualified HVAC technician check the system. They will have the proper equipment to identify the refrigerant and safely handle it. Improper handling of refrigerants can be dangerous.
