1988 928S4 - Should I convert AC from R12 to R134A??

My long time, 10+ years, mechanic says this car model should NOT be converted to R134 freon.
Does anyone else have any advice/experience? I had someone do the conversion along with installing a new compressor and the system is not cooling.
Thanks for the feedback.

Darrell

Why would you convert unless you need more refrigerant and can't get R12?

My 83 was converted because it did not cool at all. The conversion went fine and allowed for some (probably needed) parts upgrades and ease of working on by local garages, most of which will not touch the old stuff. So depending on where you are, and if you work on it yourself and can get R12, then Martin has a valid question. Otherwise do what you feel most comfortable with. It now runs nice and cool with the conversion, had a competent local shop do the work. Sounds like 2nd opinion time since you have already had the work done. There are a few good A/C voices here on the site. But it might take some diagnostics to get the correct answers. I started with my own testing gauges etc. and got some opinons here. But I ended up having someone who was not intimidated about working on a 33 year old Porsche.
I believe someone that is good can figure it out.

The reason 134 does run a little warmer than the r12, still it should be plenty cold enough, is the actual compressor engaging listen for the click, if not check compressor ,if it does click is it fast or slow fast clicks low freon slow long clicks possible hi low pressure switches, still warm check for clogs in system by icing on the lines or the evaporator., hope this helps r12 is very expensive and hard to find now days, hope this help.I will certainly convert mine if it has not been done.

YOU MUST CHANGE ALL THE O_RINGS IN THE SYSTEM or the will rot and leak and contaminate the system. I am new to this site but not to the mechanics I only own these cars one beca7se there awesome experience 2 I can work on them myself bumper to bumper, knowledge is power.