You cannot just shoot some refrigerant in and expect cold air. For example lets suppose the system has some air in it because of leaks and never being properly evacuated. More refrigerant won't help even if you could get it in without blowing your head pressures sky high. If it was converted the service ports are supposed to be changed so no one sticks the wrong stuff in and there is supposed to be a label indicating the conversion and the correct amount and type of refrigerant. If, during the conversion, the oil wasn't flushed out and changed the insides may be contaminated and plugged up. Converting to -134 in a system designed for -12 results in a loss of capacity of at least 10% and that is if it is properly done! How did you check for leaks? Do you have a leak detector or did you use some leak detector solution (soapy water)? Do you even know what your low and high side pressures are? You need a manifold gauge set to get started. If you don't know what you are doing with A/C systems you are best served by getting the car to someone who does and has the proper equipment.
David Teitelbaum
