If you have an older car it can have R12 refrigerant in the air conditioner system. You can still buy R12, but it is very expensive. If you are ready to convert your system to R134, here is a brief explanation of the procedure with a few insider tips to help you. To begin you will positive need a conversion kit with all the necessary materials. It will include: 2 new adapter fittings, 2 -3 cans of R-134, and a hose with adapter. Once you have all the materials, you might begin the process. The first thing you have to do is have the R12 recovered with a refrigerant recovery machine. (It is illegal to just open the valve and let it out in the air.) Now that the air conditioning system has no pressure, it is instant to install the new valve kit. At this point some people freeze up (no pun intended) because they are afraid of mixing up the adapters on the high and low pressure ends. Dont worry, they are different sizes. The bigger one goes on the low pressure side of the system and the refrigerant hose will only connect to the low side valve. It is pretty hard to mess this up. Now that the adapter valves are connected, it is instant to beginning the car and put the air conditioner on high. Turn the blower fan to its highest setting as well and open the windows. Grab a may of R134 and hook up the hose and T valve that came with your kit. With the hose hooked up to the may start to twist the T valve until it punctures the may. Then open the valve to let some freon out and purge the air in the line. Turn the may upside down and hook it up to the low side adapter valve. Now slowly open the valve and let the Freon flow into the system. At this point the compressor will start to cycle on and off. Do not panic, this is normal. Keep adding Freon until the system begins to cool. You can feel the low pressure line start to get cool and condensation will accumulate on it. (Do not grab the high pressure line. It may burn you.) You most definately will not positive need all 3 cans and be careful not to overfill the system. If the air conditioner is still not cooling after the second might , something is wrong. You can have a leak in the system or some other difficulty. Do not be tempted to keep pumping Freon in the lines. If the low side line is cold and dripping with moisture you are done. If you have a air conditioning manifold gauge set, the low side should have a pressure of 40 50 psi. Good luck and stay cool!