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Informed today by my local mechanic that the a/c compressor in my 380 is toast. Quoted me $1500+ to fix. Not that I can't live without a/c even in So. Cal., but this is kind of a hobby/project car for me and I would like for all original equipment to be in working order UP TO A CERTAIN POINT, as in cost. I can pickup a rebuilt OE compressor (R12) for about $180. Together with replacing the receiver/dryer, new gaskets and "o" rings, hi/lo switch and temp. sensor, etc. I'm in for about $350 (less freon/oil) doing the job myself.

Now for the questions.......would I better off converting the system charge connections to allow for the use of "freeze12" or put the whole thing together and take to a local a/c guy who can still handle R12 and have it charged?? I would prefer to be able to handle any future refrigerant needs myself if needed which is why I'm leaning towards "freeze". I pretty much ruled out converting to R134a based on the reading I've done, buts thats not set in concrete.

Any thoughts or ideas and suggestions would be greatly appreciated......this forum has been a tremendous help for all my 380SLC questions!!

Best Regards
 

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2010 Mercury Milan Hybrid, 1993 BMW 325i convertible
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6,077 Posts
Any thoughts or ideas and suggestions would be greatly appreciated
The only difference between an R12 system and a system converted to use R134 is the oil in the compressor and the fittings. The oil used in an R12 system is mineral oil, while R134 uses a synthetic.

Legally, you can't use an alternative refrigerant in an R12 system. That's why you can only find it in containers used for R134, and why you need to change the fittings. Also, for whatever stupid reason, the law says you can't convert your system only for the purpose of switching to an alternate.

Practically, there's nothing stopping you from doing it if you've got the tools and time - and realistically, who is going to know whether you had R134 in there for a day before you switched? You'll need a vacuum pump and gauge set. There are plenty of places that sell a simple screw-on R12 to R134 adapter.

The major thing I would suggest is looking at the composition of the refrigerant you're going to use. Freeze12 is just a blend with a lot of R134 in it. The performance of the system will be comparable to a regular R134 system. There are other refrigerants out there that will give you performance more like R12. Some claim to give better than R12, but I think that's marketing hype. When you look at things like boiling temperature and critical temperature, it comes down pretty much the same as regular R12, just without the cost. The other thing to look at before you do all this is whether you're going to be all right doing the service on the car for the rest of the time you own it. Going with an alternative means no AC shop will touch it as long as you've got the blend in there. Don't try to fake them out, because you'll be contaminating their whole supply of refrigerant and that will cost them hundreds (maybe thousands) of dollars. If you sell the car you need to make sure the new owner is aware of it. It isn't something you should do on a whim.
 

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1988 560SL 50K
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I just had to make the same call on my 560SL. Had lost most of its R12 due to a leaky compressor. Stayed with the R12 but my normal shop is licensed which helped with the decision.

R134 just does not cool as well as R12 and SLs are not known for having the coldest systems to begin with.

R12 is still available. With a lot of folks converting it just leaves more for the rest of us.

A long time MB certified mechanic told me that products like Freeze12 will work to start with but will damage the compressor after a few years.

R134 having a smaller molecular structure will tend to leak in places R12 will not. Something to keep in mind on old system. (not sure if true – came from the R12 proponent)

Remember that if you convert to R134 and you don’t like it – converting back is just as much work and costs as much as converting in the first place. Since it is very doubtful you will find someone to do it… it really is a one way street.

So..I’m sticking with R12 as long as I can.
 

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1978 280slc
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As a joke could someone tell me how you oil these things(R12 compresson). Hell if I mess up I'm in the same boat as I was to begin with, a non-functioning AC. I tried spinning the clutch and it feel not so much seized as it is sticky because it still moves. If I could get some new oil in there and rock the thing back and forth maybe it will let loose, then all I'd have to do is get all the wiring and hoses repaired and have the system recharged with freon. I know my system held refrigerent until it all came out a hose so maybe the system isn't as shot as I thought it was. I should mention that it's 90F here right now so maybe my decision making is clouded.

Good luck on getting your AC system working, all mine is is an obstruction to the radiator and a front end ballast. Better start saving my money!
 
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