I am rebuilding a 1975 115 model 300D. Having sat for 6 years I am sure the AC system is empty. I thought that now would be a good time to convert it to R-134. I would like to keep it an R-12 system because everyone I know that has converted to R-134 complains that the new system doesn't cool as well as the R-12. But, by the same token, I was not interested in paying God knows what for the R-12.

I spoke with a German MB mechanic in San Antonio about this conversion and he assured me that I had to replace the York piston compressor with a rotary one. No mention made of the condensor or any other equipment replacement other than the dryer.

Today I spoke with the head man at the local auto AC supply house in Corpus Christi and he said that the York compressor was acutally better than many of the rotary comp. on the market today and that it was absolutely able to handle the R-134.

Secondly, he said that the main reason that conversions don't cool as well is that the old copper condensors are retained. He said that these cond. are not designed for R-134 and will not cool as well as the newer aluminum ones.

Newer cond. have many more, and smaller tubes, and they have tubes on either side rather that using one continous tube. He also said that when you change the cond. be sure that you get the biggest one that will fit in front of the radiator and that you seal the area between the cond. and the rad. so that there are no outside air leaks, i.e., all air that goes to the rad. must go through the cond.

He mentioned an R12 substitute called Freeze 12. It is considerably cheaper that R12 and can be used in R12 systems. He does not handle Freeze 12 because he feels that it is better to convert the system, but he says that he has not heard any negative feed back on it.

I would be interested in hearing any comments of R12/134 conversions.