Before 1995 most vehicles came with R12 refrigerant in the air-conditioning system. If your air conditioning is no longer cooling as well as it once did, then chances are you need to recharge the refrigerant in the system. Recharging an automobile air-conditioning system is rather simple, however, R12 refrigerant is difficult and expensive–you must be a licensed professional to buy it. Instead you can convert an R12 system to an R134a system with a few parts and some basic tools.
Discard any R12 refrigerant still in the system by taking your vehicle to a licensed air-conditioning professional. Releasing R12 directly into the environment is dangerous and punishable by law.
Open the engine compartment of your vehicle. Find the high and low side service ports for the R12 air-conditioning system. Push the low side retrofit R134a fitting over the old fitting and use a wrench to tighten it. Torque the fitting to 20 foot-pounds.