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  #1  
Old 08-29-2001, 04:39 PM
moedip
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R-12 to R134 conversion

Bought a couple of R134 retro kits. I converted my wife's VW 2 weeks ago - added the ester oil and R134. It works great. Read a thread on this forum where a fellow had a compressor grinding inside and has a major repair on his hands after retro R134 kit was installed. The manufacturer of the retro kit states that as long as you are recharging a closed system - the old oil will flow to the lowest place and it won't do any good and it won't do any harm - it will just be there to be removed when service is needed in the future. The new ester oil will coat all rubber parts and make them usable with the r-12 rubber components and R-134. I know the kit worked good on my wife's VW - but did the retro kit cause the other fellow's compresser to break apart inside or was it coincidence?? Has anyone done this kind of inexpensive R134 retro on a Mercedes with success - or should I not attempt it on my "baby"?
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  #2  
Old 08-29-2001, 06:04 PM
Joe-1
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Dont convert it if it isnt leaking

If it aint broke, dont fix it. My 16 valve isnt cooling as well as when it was r-12. I have a total conversion, o-rings, compressor, and 20 ozs of 134. I tried the 85% rule and it doesnt get as cold as when it has 20 ozs. Joe
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  #3  
Old 08-29-2001, 09:20 PM
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I bet threads like this start to vanish as we get closer to winter months!

Coming soon to a forum near you: "Help: heater not working" and "Help: windshield fogging up"

He he he... :p

- Nathan
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  #4  
Old 08-29-2001, 09:48 PM
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Lightbulb The Archives Are Your Friend...

Moedip,

Use the search feature to comb the archives with topics like: R-12 to R-134a conversion, AC retrofit, AC recharge, and the like. I hope you will have a lot of time to read all of the threads you will find.

This conversion is one of the most hotly debated topics on these forums. Others include: oil change intervals, regular motor oil Vs synthetic, engine and fuel additives, antifreeze - green Vs amber, and that's just the ones that stick out...

Bottom line, some members have had success with the conversion, others have not. The basic deal is this. If your car is older and was disigned to use the R-12, the R-134a will not cool as well, could damage your older compressor that was not designed to handle the higher pressures of R134a, and it's best to stick with the R-12.

Read the archived threads and tell us what you decide, and what influenced your decision...
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  #5  
Old 08-31-2001, 09:11 AM
LarryBible
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The most important thing is to put in the ester oil, otherwise you will mostly likely lose the compressor.

I have found that one of the downsides to the kits is the cheap adapter fittings leak quite often. If you go to aircondition.com they have brass ones that are much more substantial.

I agree with Mr. Carter, the a/c posts are rapidly coming to an end for this year. Even in Texas we are almost ready to get out the sweaters, it has been 71 degrees or less every morning this week when I got in the car. But don't forget to get those A/C's tuned up before the first hot day next year.

Have a great day,
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  #6  
Old 08-31-2001, 11:30 AM
Bigshot
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still hotter than hell in FL! I dream about opening the sunroof on my new ML, not till October(maybe).
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  #7  
Old 08-31-2001, 12:02 PM
dsantos
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Thumbs up

Moedip,

I did the 134a conversion on my wife's 89 300e. It works fine. The conversion was done this past Feb 2001. I purchased the $39 conversion kit from Wal-mart. It included the adapters, oil, and 134a.

I had spent BIG bucks on the AC about 2 years ago. A hose, ~$600, had a leak in it. So it was replaced and recharged with R12. That worked for about a year, then sure enough it started to blow warm air again.

I searched in the forum and saw that some people did the conversion without any compressor problems. So I figured I'd give it a try. Most of the R12 had leaked out so I didn't bother having the system evacuated. There was no pressure on the schauder valve so I figured not much R12 was left.

I followed the instruction on the retro kit and installed the 134a and oil. If I remember correctly, I used 2 of the 3 cans of 134a. I used the supplied pressure gauge to make sure I did not over charge, remember to only charge to 80% of R12 capacity.

Got in and sure enough, cold air was filling the cabin. Now this was in Feb in North Carolina. The big test was how it would perform in the hot and humid summer.

Well even in 100 F 80% humidity, the AC works like a charm. My wife is very happy. Especially since it only cost $39 and not $1000+. I check the pressure monthly and have NOT had to add any R134. I don't know if this is due to the larger molecule or if the oil sealed the leak, but I am very satisfied with the conversion.

It DOES NOT cool as well as the R12 did when it was working or as well as my 134a in my 1992 400e, but we are talking maybe 4 or 5 degrees difference, and THAT is on the hottest days.

As other members have pointed out, this is a well covered subject. Do a search and look over the data, that's what I did. If you do decide to do it, then good luck and post your results.
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  #8  
Old 08-31-2001, 12:11 PM
moedip
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Thanks David

I appreciate your post. My wife's VW had the same Walmart R134 done to it and it works great! I was just concerned after reading a couple of posts from 2 guys who said that after they did it their compressor started grinding a while later causing what sounds like a major clean out and new compressor. I am trying to find out if it was coincidence or the result of the change over that caused their compressors to go.It sounds like they did add the ester oil. I would hate to do this retro to my BABY only to have a major disaster later this year or next year. Has anyone had this retro for more than a year with no problems???
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  #9  
Old 08-31-2001, 01:25 PM
LarryBible
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I admire the initiative and thriftiness of doing these convesions, however, it is really important than when changing over, you evacuate the system as much and for as long as possible.

It is imperative that you remove all traces of R12 AND maybe even more important that you ensure that there is no moisture in the system. Moisture will combine with the refrigerant to create an acid that will eventually corrode the system from the inside out. This is particular important on most MB cars because of the huge amount of work involved in changing the evaporator which is the component most likely to be attacked by such corrosion. Changing the filter/drier during conversion is also a very worthwhile step.

Good luck,
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  #10  
Old 08-31-2001, 10:57 PM
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Moe...

I talked to several AC shops and independent mechanics about this issue at the beginning of summer. The consensus was that there are at least two different compressors used in older Mercedes'. Neither is suited for the higher pressures created by using R-134a. My sources told me that the compressor would not last longer than two years after a conversion.

I can't recommend this procedure as long as there is any doubt about compressor life. Anyone on the forums who has done these conversions that has had one still working after two years should post their results so we can be more confident of the longevity of this type of program.

Also, I would strongly agree with Larry about evacuating the system, and even considering replacing the dryer and accumulator.
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  #11  
Old 08-31-2001, 11:14 PM
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Greetings,

I have done this conversion on my '80 300TD. Actually I did a complete replacement on major components because they were missing on my vehicle when I bought it. Stolen I suppose. I replaced the evaporator, lines, and the York compressor on mine from a salvage yard. I remembered to replace all the o-ring seals with the new R134 green ones as well as added a new filter/dryer before evacuating the system. If your system is totally dry of oil I would not follow the kit instructions of adding two cans of R134 before the oil/R134A mix. I would fill with the R134A then use the oil mix right after that. There's no lube or very little in the system and there is a possibility of locking up the compressor from lack of lube. The initial can just applies pressure to the switch to allow the compressor to actually start turning, but it's straight freon without lube. Try it my way and you'll end up with better success as well as a lubricated compressor. If you keep an eye on your sight glass it will tell you when the system has recieved enough freon, bubbles disappear, this is your full point, or 85% point. Shut off the freon flow and allow the system to run while still watching the sight glass. If bubbles reappear shortly there after add small amounts until it remains clear while running. You won't use the entire kit that you purchased, if so you probably over charged the system. Since June when I did mine it has been leak free and serving me well. When temps exceed 95 degrees it will not cool nearly as quick as R-12 did, but saved me money in the long run. These older Benz's just don't have the larger evaporator required to get the same effect that R-12 has on the system in hotter climates.

Charles
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Last edited by can-do; 09-02-2001 at 01:27 AM.
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  #12  
Old 08-31-2001, 11:54 PM
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Location: Los Angeles, Calif, USA
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The sight glass is reliable. It will be better if you have a way to measure the amount of R134A going into the system, 15 to 20% less than R12. I use an electronic charging scale. Ebay has them. Here is one from ebay:

http://cgi.ebay.com/aw-cgi/eBayISAPI.dll?ViewItem&item=1632730091


David
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  #13  
Old 09-01-2001, 10:41 AM
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My shop has done near a thousand R12 to R134 conversions. I personally hate them and keep my best customers from making that decision.

We have been doing this for ten years and have changed many of our practices. The most significant is to change from ester to PAG 46 for Nippondenso compressors. We didi this at first to stay with MBs warrantee requirements. Later after much discussion and research we decided that the viscosity of the ester oil was wrong for those compressors (Its all right for the GM R4 and A6 compressors and we still use it there). Our retrofits are much more successful now that we have changed. I say that after almost two years and two summers worth of experience with the new procedure.

I smile as I read of individual success stories. After about the first 700 retrofits, I finally had enough feedback info to draw a number of conclusions:

1) They absolutely DON'T cool as well. Maybe close in 75% of cases.

2) They will take out at least the compressor seals within two years (If a new compressor is not installed at the same time).

3) They get worse over time and can not be repaired without wholesale replacement once they get to the real poor condition. I have presumed many of these problems are due to chemical insulative properties aquired through oil/flush, oil/oil, oil/refrig, refrig/refrig instability. I got a call the other day from a top BMW tech in Pittsburgh. He wanted my Southern experience on retrofitting as BMW says not to do it on certain aluminum evaporators because of a corrosion problem. I told him not to worry and then started to worry myself. I have vast experience and it is insignificant in so many ways when it comes to long term evaluation of re-engineering a system.

BTW, our shop 280TE which was our guinea pig, still works marginally on the new compressor and retrofit we put on it in 1991 (the York was replaced with a Sanden), with no additional work. We retired the car two years ago and one of our techs still drives it.
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Last edited by stevebfl; 09-01-2001 at 10:47 AM.
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  #14  
Old 09-01-2001, 10:51 AM
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Sure am glad I squirreled away 3 cases of R12 while it was still available.
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  #15  
Old 09-01-2001, 01:10 PM
LarryBible
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Paul,

I too squirrelled away some R12, a 35 pound can, but it's almost gone. I have reluctantly resorted to converting to save the R12 for my 300E that I don't want to convert when the time comes.

Steve,

Thanks VERY MUCH for sharing your experience with us. I think that 1,000 conversions is sufficient data to consider this as valid information.

I am forced to convert my daughter's 300D to r134. It has an R4 compressor and I'm glad your experience with ester in these has proved to be somewhat successful.

My curiosity is peaked though, I was told a long time ago not to use PAG in a retrofit. Is this only acceptable if the system is COMPLETELY flushed and new filter drier used?

Thanks again for the info.

Have a great day,
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