Important Warnings:
* Do not attempt to add refrigerant yourself unless you have the proper equipment and training. Improperly adding refrigerant can damage the AC system, and the refrigerant itself is under high pressure and can cause serious injury.
* R-134a should only be added with the help of a qualified technician using proper AC service equipment including gauges. This equipment measures system pressure to determine the amount of refrigerant needed and ensures the system isn't overcharged or undercharged. Simply adding refrigerant without knowing the system's charge is extremely unwise.
* Leaking refrigerant should be diagnosed and repaired before adding more. Adding refrigerant to a system with a leak is a waste of money and refrigerant, and is environmentally irresponsible.
Find a qualified automotive air conditioning technician to service your vehicle's AC system. They have the tools, knowledge and safety equipment to properly diagnose and repair any issues.