Originally Posted by LarryBible

Although I am not a fan of refrigerant conversion in spite of the fact that I've done a number of them, it CAN work in most cars IF done properly. Simply installing fittings, evacuation and charging is NOT doing it properly.

For proper conversion, you need to AT A MINIMUM, put in the proper amount of Ester oil, change the filter/drier, evacuate the system and charge with 134 beginning with 70% of the specified R12 volume. You then monitor the system closely and if necessary add one ounce of refrigerant at a time until the system is cooling properly. You also are CLOSELY monitoring high side pressure to see that it does not get too high. In most systems 250 high side is on the edge of too high.

I have only started this method recently and have been amazed that the proper volume is as little as 70%. Too much will kill the performance of the system.

The BEST way to do this is with a charging scale that gives you have ounce resolution. The point where the system is over charged is a very fine line, that's why you add only a half ounce or one ounce at a time while monitoring high side pressure to see that it doesn't "run away."