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  #16  
Old 09-01-2001, 01:48 PM
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Join Date: Apr 2000
Location: Falls Church, VA
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I am now through most of my second season after my epic battle to convert to R134. Starting with a fried compressor, I did a rebuilt Nippondenso from Partshop, new manifold hose, drier, sensors, and Schraeder valve. I had the system professionally evac'd and charged.

System is still working. It has a small leak and I top it up once every six weeks or so. Concur with Steve about the cooling, but it works for me, mainly because the car is in a garage at work. It would be a very different story if it sat out in the sun all day.

I am personally satisfied with the results and glad I did the conversion. I feel like a real AC guy with my little kit from Pep Boys.
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Chuck Taylor
Falls Church VA
'66 200, '66 230SL, '96 SL500. Sold: '81 380SL, '86 300E, '72 250C, '95 C220, 3 '84 280SL's '90 420SEL, '72 280SE, '73 280C, '78 280SE, '70 280SL, '77 450SL, '85 380SL, '87 560SL, '85 380SL, '72 350SL, '96 S500 Coupe
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  #17  
Old 09-01-2001, 02:30 PM
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Larry,

I have been doing this so long that I have heard more don'ts than I can remember. I have also seen most of them turn out to be fable. I have always only retrofitted cars which have been flushed first. This really means that I only retrofitted cars that I was already going to flush; mostly cars getting new compressors or evaporators.

Originally there was great fear of mixing either oils or refrigerants. The consensus now states that the mineral oil just sits around as mentioned above. I have heard that PAG lubes better than ester, but I have heard that ester works better in non-flushed systems. The plain success of so many amateurs points to the lack of problems with the mixtures.
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Steve Brotherton
Continental Imports
Gainesville FL
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33 years MB technician
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  #18  
Old 09-03-2001, 01:22 AM
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Posts: 166
There is an automotive air conditioning bulletin board that is comparable to this site on MB automobiles. The amateurs and DIYers ask the questions and there are professional techs who provide the answers. Try:

http://www.aircondition.com/wwwboard/

In general, they refer to the inexpensive kits as "death kits" and say their experience shows that somewhere between two weeks and two years after installing one, you will be replacing virtually every a/c component forward of the firewall.

There is a wealth of information on that board about automotive a/c and how to do the conversion from R-12 to R134a correctly; what oils to use, how to flush out the old oil, changing o-rings, etc.

One thing they say is mandatory in making the conversion is replacing the accumulator or receiver/dryer with a R134a compatible unit; otherwise the old dessicant will eventually spread itself throughout the system, ruining the compressor and requiring a lot of work and money to correct.

I would urge anyone interested in doing his own a/c work to spend some time reading that board. You can spend hours gleaning valuable information.

Hope this is helpful.
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  #19  
Old 09-04-2001, 11:49 AM
moedip
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Thanks to all - nothing like being armed with information before making a decision - I have sure learned a lot from this thread. You guys are great!!!
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  #20  
Old 09-04-2001, 06:11 PM
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I had made reference earlier to what I understand is a new "alternative" - R406a.

Anyone have any experience with this kind of conversion?

George
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1991 350 SDL (200K and she ain't bent, yet)
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  #21  
Old 09-05-2001, 08:37 AM
LarryBible
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I'm pretty sure that R406a is a blend of two other refrigerants. The problem with this approach is that they have different characteristics and if you get a leak, one will leak out before the other. When this happens you have to blow the entire charge, evacuate and completely recharge witht the blend. There are also other considerations when charging like ensuring that you are charging in gas form to maintain the blend. If you charge with liquid you will only get one component of the blend and it will cause problems.

It may be better than sweating, but there are many service problems associated with it.

Good luck,
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  #22  
Old 09-05-2001, 12:59 PM
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How about R134a back to R12?

I had our 1988 300TE changed to R134a when doing an engine transplant that included an R134a A/C pump from a C-class.

Unfortunately, a big black Mercedes wagon needs all the cooling it can get, so I'd like to change it back to R12.

I even did a visual check of the condenser of an early model (1986) 300TE (R12) vs. the late model (1994) E320 wagon (R134a) and the condenser of the late model wagon is beefier/denser/bigger.

Would I be better off changing out to the bigger condenser designed for R34a, or switching back to R12 (maybe even with the bigger condenser)?

What is involved in going from R134a back to R12?

Do I change out receiver/dryer, pull a vaccuum, change oils, etc.?

Thanks in advance,
:-) neil
1988 360TE AMG
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  #23  
Old 09-05-2001, 01:47 PM
LarryBible
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Switching either way should really be done only after a thorough system flush, but going 12 to 134 is done all the time without such a flush. Going the other way from 12 back to 134 EEFINITELY should only be done after a thorough system flush.

If you can put in the larger condensor, this should make up for the 134. If everything is holding up okay with 134 and you can get the condensor, I believe that would be a good solution to the problem. A new filter/drier at the same time along with a thorough evacuation would be some good steps to take. Don't forget the oil in the system.

Good luck,
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  #24  
Old 09-06-2001, 12:13 AM
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Location: Los Angeles, Calif, USA
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Quote:
Originally posted by LarryBible
........
There are also other considerations when charging like ensuring that you are charging in gas form to maintain the blend. If you charge with liquid you will only get one component of the blend and it will cause problems.

................

Good luck,

Larry,

Correct me if I am wrong. It should be the other way around. The blend refrigerant need to be charged in liquid form. If you charge in gas form the high temp refrigerant is coming out of the tank first (just like what you said when it is leaking). The problem I see when charging refrigerant in liquid form is that the liquid rushing into the compressor, in some case, may damage the compressor.

You will have a hard time trying to find someone servicing your system if your system is anything other than R12 or R134A.

My biggest fear of serving someone else's car is refrigerant contamination. I may end up with unknown blend refrigerant in my R12 recovery tank that will contaminate the next car I servce.

David
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  #25  
Old 09-06-2001, 08:11 AM
LarryBible
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David,

Thanks for the clarification. I knew that there were downsides of some description involved with the blends.

I have always TRIED to be careful allowing liguid into the system when charging an automotive air conditioner. This seems to especially be true with the old York/Tecumseh compressors, you could knock out the valves in them by leaning over the radiator too abruptly.

Thanks,
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  #26  
Old 09-06-2001, 08:37 AM
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Pouring liquid into the system works just fine, IF the motor isn't running. One must have good measuring equiptment to do it that way.
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Continental Imports
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