A/C Recharge

[msark]

I have a 1991 964 and every 2 years or so the R12 freon goes away.

It's way to expensive to recharge anymore and there hasn't been a leak detected in the past. My shop says that to go 134 I should change the drier. 134 seems less effective and corrosive. I was told by a friend about Freeze 12 and Autofrost as alternatives which he has used in his vintage muscle cars without a problem. And it seems to be cheap!! Thought or experiences?? Thx... Mark

[gizmofixer]

Our cars are known to have 'porous' hoses and untraceable leaks.
I have used dye and other methods and never locacted my leaks.........
So, i have grown resigned to topping off the system every 2 years or so.

That being said, R-12 is without a doubt the best freon.
Even considering the cost, i suggest refilling with R-12.

R-134 runs higher pressures and is not as effective cooling.
You can convert to R-134 without changing any oil or the dryer.
Your tech just needs to be aware that the system will require more qty R-134 than the conversion charts show and the pressures will run correspondingly higher than a R-12 system.

WHATEVER YOU DO, DO NOT USE FREEZE 12, AUTOFROST OR ANY OF THE OTHER SO-CALLED FREON REPLACEMENTS.

These products contain propane, methane, esthers, alcohol, and other contaminants which are ineffective, dangerous, corrosive, and will eventually kill the environment, your system and possibly your tech.

[911nut]

Originally Posted by gizmofixer

Our cars are known to have 'porous' hoses and untraceable leaks.

R-134 runs higher pressures and is not as effective cooling.
You can convert to R-134 without changing any oil or the dryer.
Your tech just needs to be aware that the system will require more qty R-134 than the conversion charts show and the pressures will run correspondingly higher than a R-12 system.

The hoses in the 964 a/c system were engineered to use both R-12 and R-134a. They are not the old tech hoses that are designed to leak but are barrier hoses that operate under the higher pressures required to run R-134a.
If your car was delivered from the factory with R-12, there are 12 o-rings that will need to be changed out, as well as the receiver/drier and the fittings on the compressor.
R-134a has the ability to remove more thermal energy from the air than R-12. Usually the conversion process gets botched and improper operation is the result.
My opinion is that if you are going to spend the money to convert, go all the way. A receiver/dryer costs $30. Why wouldn't you replace it? It takes 10 minutes to drain the old oil out of the compressor. Why not do that?
Find a shop that has a reputation for working on Porsche a/c and work with them. If you can't find that, buy the "Without Guesswork" book, copy the R-134a High side pressure vs. ambient temperature graph and hand it to a good shop. If they are any good at all that's enough info to get a quality job done.

[solitude]

Can anyone recommend any Porsche A/C shop around Pasadena California? Thanks.

[msark]

Thanks for the R134 thoughts. That seems to be the route I will go. I have a very good shop here in So. Cal but they sub-out their a/c work. I was quoted $500.00 to change the drier, add the compressor fittings and re-charge w/134. It seemed like it was a bit high and there was no mention of any O rings to be changed. I would also like any thoughts on a So. Cal shop that does their own a/c work.

[911nut]

I got quoted $1500 by the local Porsche dealer. I re-charged with R-12 as I found some cans I had bought in 1980.
The next charge will be with R-134a.