Joe Rose

I'm about to convert my '92 C2 from R-12 to R-134A and although I have the factory shop manual for our series, I don't seem to see all that much information about the A/C system. I know among other things I've seen in online posts that I have to change the receiver-drier (accumulator, I guess), and I also have to rid the system of its mineral oil and refill with esther oil. My question is since I don't have the Porsche service equipment to do this, how do I drain and then refill the compressor? Any suggestions, tips, etc. from people who have done this conversion would be most appreciated.

Jacke2c

https://griffiths.com/porsche/air-conditioning/

If you are converting you need to find out if your evaporator is still good, expansion valve etc. I completely rebuilt my system using instructions from Griffiths. i flushed all my lines and inverted my compressor for several hours and turned the compressor crank shaft and refilled with ester oil since it mixes well with the old oil. My system cools to about 38 degrees all the time consistently and i am very happy. I replaced my evaporator with one from Griffiths. A pain in the butt job, but well worth it since you get the opportunity to clean the whole system.

tbennett017

Yes the stock R-12 evaporator isn't as good at 134A. If you're going all in, I'd agree with @turbotwoshoes.

I did a total rebuild a couple of years ago... but I left the drain/evacuate/refill to the pros. I took the car in and had it cleared out.. did the work, then took it back.

Joe Rose

Thanks, fellow Rennlisters, for your input. I appreciate it very much. I have an A/C vacuum pump, manifold and hoses for 134A and a ton of 134A which I bought in 30 lb cans several years ago. My system still works rather well with R12, but since I have the 134A and most of the tools I need, I think I want to convert it now. Without a recovery system, however, I'll first take my car to a friend's shop that has such a device to remove its current R12 charge. Then I'll see if I can do the rest in my own garage. Thanks again for the help.

aceking4u

Did your AC ever worked at all since owning the car? I would love to hear the feedback from before and after (when working). I guess I got lucky with my car w/ working AC.

Joe Rose

Yes, my A/C has worked decently as long as I've had the car. I just want to convert it now because R12 is hard if not impossible to find and I bought a large quantity of R134A a while back. I know there are drop-in replacements for R12 and I tried one in a friend's 911SC a few years ago, but I was not that pleased with the result. When I make the conversion and assess its performance, I'll post here with my impressions.

JasonAndreas

Have you seen TSB 9501-8717 "Retrofitting R12 A/C System to Refrigerant R134"

A914MAN

I've been told there's a refrigerant for appliances and auto use that's compatible with R12, but I wonder if this is urban lore.

My A/C doesn't blow cold. It all seems to work, but I'm sure it's low on refrigerant. I think I've got a 30 yr old can of R12, anyone know if that would still be useable?

I'm sure I need to replace the reciever/dryer if I recharge with said R12 but that's new territory for me. Are the economy R/D's good enough? If I'm lucky maybe I can get two seasons out of the charge before I've got to bite the bullet and upgrade the evaporator and go to R134.

Keeping an eye on this thread

JJJMCD

Don't do it - the 964 A/C system was designed to work with R12 and is marginal as is. It will work less well with 134A. New old stock cans of R12 from the 1980s, which work perfectly fine, are readily available on eBay. I just converted my A/C system back to R12 after an ill considered 134A conversion around 10 years ago and it works much better now. BTW, this is a job for professionals- don't try to do it yourself

tbennett017

Totally disagree with JJMCD. Mine runs 134A just fine. I did however replace the evaporator, Receiver/Dryer, and all associated seals. It exceeds the cooling spec and works great on 104+ days.

Except for the gas removal/charge, I did the rest myself.