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Old 11-22-2005, 04:37 PM
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Join Date: Mar 2001
Location: SF
Posts: 205
R134 W124 A/C Systems........

Are the R134 A/C systems as big a POS as the R12 Freon versions? What year did the switchover take place? (1994 and up?) Are evaporator leaks still a problem on the 134 gassed verisons? Any other things to look for in a 134, (factory, not converted) How, if at all, did the W124 A/C sytem evolve given the early problems they had........Thanks Clip BTW Looking at a 94 E320 Coupe.........

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Old 11-22-2005, 04:55 PM
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Join Date: Oct 2005
Posts: 4,263
HFC134a systems are a much bigger pain than CFC12, in any area that you care to name.

The molecule is much smaller, so it leaks much easier. Any moisture causes acid to form within the system, leading to much worse evaporator problems than you would otherwise have. The pressure readings are somewhat inadequate for judging the system refridgerant level - it's best to charge by weight. The oil used is hard to even call oil, and it certainly does not lubricate the compressor nearly as well as the mineral oil used with CFC12.

The only advantage that HFC134a has over CFC12 is that you can go buy it at your local discount parts house without a licence.
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Old 11-22-2005, 07:37 PM
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Join Date: Jul 2005
Location: Eastern Panhandle, WV
Posts: 43
The price of R12 has dropped dramatically because of decreased demand. R12 will probably be around for a long time. Only downside as mentioned above is that you need a license to buy it. If I were you and the '94 still has R12 (but I suspect it may be 134A), I would keep it that way. Evaporator failure is a known problem no matter which type of refrigerant. The rest of the system seems reliable but like anything else, as it ages, it will need service. My '90 300E had the evaporator replaced 4 years ago. The receiver/dryer and expansion valve were replaced (as well as vacuum motors) and the system was pumped down to check for leaks - none! Original compressor and 4 years later still cools better on 95 degree days than anything newer I have.
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Old 11-22-2005, 09:06 PM
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Join Date: Jan 2005
Location: Minnesota
Posts: 975
the 94's had 134...the evaporator is an issue, but its an "if" not "when" type of thing. Not a guaruntee that it will leak, just a probable. Other than that, it works adequately. I think most would say its underpowered compared to the AC systems of most cars today, but it still cools the car without problems.
Daily Driver: 02 E430 4MATIC
In the family: '03 E500 // '04 ML500 // 64 220SE
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Old 11-23-2005, 10:55 AM
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Join Date: Jun 2000
Location: Plano, TX
Posts: 2,527
The '93s all had R-134, and so did '92 models with v8 engines.

I find the 134 cars to be at least as reliable as the earlier r-12 cars. MB upgraded to dual electric fans with a full shroud and moved to a larger displacement nippondenso compressor. A/C performance is very strong in these cars. My 300E 2.8 blows so cold it can be uncomfortable - this in 100 degree heat.

Anecdotally, my 1993 just now requires its first a/c service and repair. The expansion valve has developed a slow leak, so it need to be replaced. Other than that, the a/c has worked great for the last 12 years, and has never required any attention.

- JimY

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