Alright here I am with learning about air conditioning. I got a book and read it. I was thinking of just putting it under my pillow and sleeping on it, but reading was only slightly less confusing.

Then I hung out at a local shop where the guy gave me some helpful tips. I now know what the various components are, how to identify a R12 from a R134a system and where the low and high side of the units are.

To date I have outfitted the shop with some new tools - a dual gauge set (very nice from Harbor Freight), a new vacuum pump and a Robinair R12 recovery system. I plan on doing mostly R12 work, but the gauge set works on both. It took getting an adaptor from the recovery unit.

So here are the questions.

1. Oil in the compressor. As I understand it, an air conditioning system is supposed to have oil in it - about six ounces. Yet when I look on the compressor there is no drain hole? The instructions of the recovery system says to keep track of the oil extracted and add that much oil back in.

If there is no oil drain then how is the oil removed from the system?

If you are new to a system with no Freon how do you tell how much oil is in the system?

I evacuated a system with almost no Freon in it (R12). The car has been sitting six years with the system closed. When I evacuate the system, I can pull and hold a vacuum over night. Do I now just put Freon into this system or do I have to add oil?

I got a conversion kit for R134a. In the instructions they suggest having a authorized shop extract the old R12 if there is any in the system and then just filling it with R134a. The kit they provide is R134a with oil and some seal conditioners. They make no mention of flushing the system first or how to remove the old oil?

If you want to add oil only how is that done?

At the store they were selling a flush kit, but this assumed that the system was open and the components could be washed internally before assembly. Do I have to flush a system before putting in R134a.

Finally I have this great recovery and reclamation system. After it extracts the R12, which it does automatically, there is a filtering mode that cleans the Freon in the tank. All good. But then I want to reuse the Freon. There is nothing in the book about using the Freon from the 30 pound tank. There are two valves on the tank and an attachment for a yellow hose.
Which valve do I attach to - the Red or Blue one to put the Freon back into the car? What is the connection for the yellow hose for?

Thanks much. I am sure these are probably mostly silly questions, but I do not want to waste a bunch of recovered Freon or to mess up a system only to have it fail a few thousand miles down the road.

Dan the Pod Guy
Portia's Parts


Sounds like what I did when they wouldn't let you buy R12 anymore without a license. I bought a recovery system, got a license and hung out with the old a/c guy down at the shop.

I have three tanks, not sure if they are 30 lb or bigger. They each have a blue valve and a red valve. My red valves say liquid and the blue say vapor. I've always used the blue valves for recovery and reuse. Don't have a yellow--that must be new.

As far as the oil. No idea how to measure what comes out, unless you have an oil separator. The oil usually circulates with the Freon, so some comes out if you pull out the Freon. From what I understand, if there is no Freon, the oil lies wherever it falls. So, if you replace a condenser, you add that much oil back, whatever that proportion is, plus some for whatever you think has leaked out. Doesn't really seem to be an exact science, at least I never found out, just went by what the a/c guys said.

I guess if you flushed the whole system, then you could add the recommended amount for that system.

I've just added the oil through the plug on top of the compressor, before recharging.

I've heard that the new 134 oils are compatible with the r12 oils, so, maybe no need to flush?

On your 6 year sitter, it sounds tight if it can hold a vacuum over night but what happened to the Freon? Unless you notice a lot of oil around the joints, I wouldn't add too much oil. I think a couple of extra ounces of oil wouldn't hurt but having no oil is certainly a problem.

DanT 85 928 replaced the bad a/c line a few years ago, put a couple of ounces of oil in and recharged--good as new


From Tech bulletin 8700 9206 on R134a Conversion (also see 8701 # 9205 and 8701 # 9208)

Refrigerant R-l 34a and refrigerant R-l 2 ARE NOT compatible with each other. Care must be taken to identity the refrigerant type before servicing or making any repairs. Many of the components in the R-134a system are different from those used in A/C systems using R-12. Always consult the latest Porsche parts microfiche before ordering or replacing parts.
This will help prevent any possibility of damaging the A/C system. The refrigerant oil which is used in R-134a A/C systems is also different it is a synthetic oil marketed by Nippondenso and is the only refrigerant oil currently approved for use in Porsche A/C systems using R-l 34a. See Warranty Bulletin Number 9221, dated August 13,1992 which outlines the Warranty Part Numbers to be used for Warranty Claim Reimbursement. All A/C systems and components charged with R-134a have been marked accordingly. When servicing A/C systems using R-134a refrigerant use of specialized recycling equipment is required. Porsche Cars N.A. currently recommends the Sun MRC 450. Refer to Equipment Bulletin Number 9202

So the old mineral oil for R12 is not compatible with the R134a and although some people don't flush their system during the conversion - it is recommended.

I've got the Tech Bulletins and Porsche AC System stuff as pdfs from the Morehouse Cds if you don't have them let me know.