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Old 04-21-2002, 08:58 AM
GregS GregS is offline
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Join Date: Apr 2000
Posts: 459
JOE P: Can you tell me exactly how much oil I should put in my '84 300D when I convert to 134a? And about how much gas?

MRWITH: Here is a quick review of what you need to convert to r-134a:

PARTS: all new (green) o-rings, new receiver drier, expansion valve, 134a-specific valves that screw on top of the r-12 shrader valves (I'm refering the valves with which you evacuate and fill the system), cans of gas, a bottle of oil


-no matter how successful an r-12 system is converted, 134a will never perform all that well sitting in traffic. You won't start sweating, but you probably won't feel cold either.

- for lots of general information on this topic, start searching, which is a terrific webpage on automotive a/c

-the sponsors of this page, and, sell everything you need for your a/c system and are extremely knowledgeable

-one of these sources has rebuilt r-4 compressors for $134! Keep in mind that your compressor that has run for years on r-12 probably will not last long on 134a. THis is a somewhat debated issue, but the fact is, 134 does require higher operating pressures, and if your compressor is the least bit weakened with age or wear, you will find that it can't keep up with system demands, and the end result is you have bad a/c, and you are sitting there wondering what went wrong. I would just replace your compressor. If your system already doesn't work, it is probably already bad, if not just from sitting there from lack of use and oil starvation.

-DO NOT try to do this job without a proper vacuum pump and gauages. I happend to pick these items up cheap through the local paper, but a vacuum pump that will actually do the job costs around $300 new, and a set of gauges can be picked up at Pep Boys for around $50.

-Because you probably don't want to go to the expense of buying the pump and the gauges, I would recommend you replace all the components yourself, and then take it to a shop to have a vacuum put on it and filled with gas. Maybe you can check a local rental store to see if they have a vacuum pump??? If you are in the DC area I would let you borrow mine.

-As someone else mentioned, ignore the sight glass completely, it means nothing!!!! With a/c systems, the ONLY thing that means anything are the high and low side operating pressures. And this is why gauges are vital. You CAN NOT do real work on any car's a/c system without gauges. Generally speaking, you are looking for pressures around 180-190 high side and 30-40 low. But these pressures vary depending on the car and outside temperatures. High side pressures should be around 2.5 times outside, ambient temperature. Too high=poor cooling and death to your compressor, too low=poor cooling. Bottom line is? Get gauges, don't try to guess, and ignore that sight glass!

-in order to do the job right you need to blow out every component with a blow gun and mineral spirits. After you have blown the mineral spirits through and made sure it is comming out clean, blow just air through for a while to make sure all the mineral spirits are blown out and the component is dry.

-the best oil out there for a completely clean system with a new or rebuilt compressor is a Texaco HFC100. Get it at If you are using your old compressor with 134a, use PAG oil, NOT ester oil. The oils can be injected into the system with a turkey baster. All the o-rings need to be coated with the oil before installed.

-lastly, you do NOT need a parallel flow condensor. This was just my suggestion to the guy asking how he can optimize his system, but that is not to say your original condensor won't work too.

I think I covered everything. If there are any more questions, I will try to answer them, but you should really start going to, which is where I have collected most of my information.

One last fantastic info source is this saab technician's page (I am somewhat of a Saab feak too :


Hope this all helps.

'84 300D
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