LeMans71

Nick, your '83 would definitely be an R-12 system. It is my understanding that R-134a wasn't mandated until the '90's - so some (all?) of the 968s may have it, but I believe all 944s are R-12 - unless of course a PO has done a conversion. It's enough of a procedure/expense that it would probably only show up only on a well-loved, documented car. Supposedly, R-12 is a better refrigerant, but the supply is limited and it's quite expensive. Also bad for the ozone layer, which is why it was phased out. R-134a is available in cans at any auto parts store, so you can charge your system yourself.

austin944

You can buy enough R-12 on Ebay to fill the entire system for around $90. Like this completed auction, for example:
http://tinyurl.com/4hwq9c

You will need an EPA license to buy R-12, but it's very easy to get:
http://www.epatest.com/

Then you need the system evacuated, and a can tap and optionally some gauges, and you're ready to start charging. Of course this assumes there are no leaks -- I would recommend a leak test if you're low on refrigerant.

Charging the A/C was surprisingly easy for me.

bluedevil

Hey, I think I can help you with some of the used AC equipment. I am in Victorville and just had (still having due to some problems) my AC worked on. I have a box of equipment (no compressor) that I would be happy to sell you. I was about to ebay the stuff but happy to sell it to you and I will be out in Vegas soon so email me if your interested.
What shop in Vegas is doing the work, I only know of one good Porsche shop in Vegas right now?

dacula951

Sorry for the delay in getting back to this.

For dry nitrogen testing, you need to get ahold of a bottle of compressed nitrogen. I bought one (40cubic feet I think) at AirGas for about $85. Then you'll need a regulator to regulate it down. I actually bought a fitting to adapt the nitrogen bottle to the oxygen regulator I have for my cutting torch. The max I can regulate with it is 100psi but I think that is good enough. You can then connect the output of the regulator to your manifold guage set. Fill it up to 100 psi and let it sit overnight. If the temperature of everything is stable you should see no loss in PSI. This method is much better than vacuum tests because full vacuum is only equivalent to about 14 psi and is the reverse direction of what the system will be operating under. Also, if there is any remaining refrigerant disolved in the oil it will slowly boil out under the vacuum and you may get a false positive for leak detection. Therefore vacuum testing for leaks is pretty worthless.

Another benefit of having a nitrogen setup is that you can purge your system with the dry nitrogen when vacuuming the system prior to charge. What I usually do is vacuum the system, fill with dry nitrogen, then vacuum again. This reduces the likelyhood of having leftover moisture.

If this is true, then you have almost no refrigerant left. If some was left the compressor would at least turn on momentarily.

You are correct that a rough estimate of the charge level can be made by checking the operating pressures. What I was referring to was the static pressure. The static pressure in the system, provided it is pure R12, will only be a factor of temperature. The amount of liquid refrigerant in the system will not be a factor. If you were to release some R12, the pressure would drop only momentarily because additional R12 liquid would boil off and the pressure would go back to where it started.

m73m95

wow, thanks Dacula.

Very informative!

KuHL 951

That is one downside but it works great for those of us that do their own AC work. If you had to rely on shops to fix your AC on a 944 everyone would be running R-134 and swearing at the top of their lungs every time you got stuck in slow traffic and were sweating your *** off because it works so poorly when air flow is limited across the condenser. I have mostly older cars and the Freeze 12 has been a great substitute for R-12. I still use R-12 on the 951's though, I get it from Mexico, if I know the system is tight. The oils are compatible also so you can always evacuate the system first if you had to go to a commercial shop.

F18Rep

Steve... From my little bit of experience I have found R-134 performance to be disappointing at least in my 944. And in doing some reading I saw your nearly same post over with 928 guys - that had me leaning your way (toward Freeze-12). But, one informed gent there had a good argument in that Freeze-12 is really R-134 with some small additives. This makes me think there is maybe not much difference. So, for the moment Freeze-12 is back to being option 3 after R-12 and R-134.
A quick look to EBay and it seems R-12 is about $25 a pound. Affordable but only into a system that will hold it for say, a year.

So now I read Johns post above about first testing with nitrogen. Probably a good path for me. Before I run off to spend more money, I'm wondering though if I couldn't use some thing a bit more available like LP or even welder gas. Just thinking.... Bruce

dacula951

Bruce, LP won't work for monitoring the ability to hold at a fixed pressure because some will liquify at the pressure you would want to test at and the pressure will vary a lot with temperature. Ideally you want to use something inert. Argon is a welding gas that would probably work just fine.