if you don't know how to use or have a set of gauges get some because they tell all about the a/c system most likely the freon leaked out again if you have a keihen compressor the one that has 4 squares with 4 bolts on each one you have a very good chance the compressor is toast. remember low freon will cause it to not cool and too much will cause the same problem and can damage the compressor! usally conversions uses less R134a then the R12 because it runs at higher pressure. so hook up the gauges and look at the readings if the low side is in the negitive the expansion valve is bad if it's even then the compressor is bad.