Depending on the year you may or may not be able to legally buy the coolant. Maintenance includes checking coolant level and checking for leaks. You do this by putting a meter on the valve.
First check level of coolant for any leaks. What you'll have to do is put a meter on the valve to test it. Make sure you buy the right kit for your car to recharge AC. Ask at an auto part store what kit is needed for your car AC.
Might have to upgrade to R134a if your vehicle is older than ~1992. Verify what type you have and buy a kit at any auto store to recharge your AC. Kits come with fittings and directions. Locate the low pressure side and connect the can to recharge your ac.
