964 A/C Conversion from R12 to R134
 

I need to convert my '91 C2 from R12 to R134...it is getting really hot here and I need to charge my A/C. The fittings on the compressor are easy, what I am unsure about is the Hi-Low pressure switch. No one has been able to definitively say that the switch must be replaced and if so, what it should be replaced with. Even the porsche dealer parts guy had no clue. Any help is greatly appreciated!

Do a search over in the Rennlist 964 forum on this. I've never heard it mentioned.
You will need a new receiver dryer in addition to the fittings.

Why dont you recharce with R12. Just had mine recharged last Saturday with R12 and its blowing ice cubes now.. :-)

The R12 recharge sounds great but I can't find anyone to do it. And I haven't seen anywhere to purchace. Can you point me in the right direction? Thanks!

A charge with R-134a will work equally well if done right. All 964s are designed for and capable of using R-134a.
R-134a can remove more heat than R-12. It must run at a higher pressure which makes it unsuitable for older a/c systems that don't use barrier hose.

You don't have to replace the pressure switch function, stock works fine.



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When I did mine, I put in the newer dryer, which requires different hoses. I replaced all the o-rings, added oil , and recharged. Works fine.

If you get the dryer from Griffiths you do not need to change lines. They actually sell an upgrade kit with fittings and oil for the conversion. Here is the link - they have a good question and answer page that explains the conversion process and advantages.

Porsche, 964, 993, C2, C4, Air Conditioning

Thanks, great info! I will be taking care of the conversion soon, will post how it goes.

Finally got it taken care of. Turns out it was the Schrader valve on the low side port that was leaking. Through some pain in procuring the right adapters, it is blowing as cold as ever. Thanks for the advice!

Oh, I guess it is not over. As Lee Corso would put it, "not so fast." I apparently have a another leak. I turned on the A/C the next day and it was not very cold, although the compressor did Kick on. The day after that the compressor would not kick on at all. So, now I have to start over and search for the other leak somewhere else in the system...yeah me!

Usual suspects are: evaporator, compressor and condenser

anyone have a conversion chart for R-134 from R12 on both 964 & 965 cars??

Both cars have identical major components. The lines in the engine compartment are different on a Turbo than a n/a car.

i meant freon levels. I think I read 660 grams or so at one place. I recently had mine topped off by it barely budged the output: cools to about 75d on a hot day at best...I think the amount is shy of what it should be.

M.

Per the "Without Guesswork" book:

R-12 930 g
R-134a 840 g

ah, that could explain things...:/