I did a conversion on a W124 from R12 to R134a, and I had to do it twice in order to get the same cooling efficiency I had with R12.

The second time around, I changed both the condenser AND the A/C fans (from single to dual) to the versions used with the FACTORY designed W124 R134a A/C (already did hoses, expansion valve, dryer, and A/C compressor).

Since R134a is NOT as efficient as R12 (all things being equal, e.g., using the existing condenser, etc.), you will need MORE airflow (esp. when not at speed) to get the cooling efficiency you had with R12.

:-) neil
1988 E36T AMG
1993 500E

The variety of opinion on the effectiveness 134a conversions and the materials needed probably reflects the variety of human tolerance for heat and humidity as much as it does the variations in climate where used or the type of MB that is being converted from r12. As I indicated in my post, your results may vary, and after all, the initial request was for anecdotal information from those who had tried the procedure.

Larry Bible's remarks are worthwhile to consider as they are the valuable experience of a certified tech, but we all should probably consider this: as r12 vehicles get scrapped, the drop in r12 price (which I have not seen, but this is Montana) is very likely to be followed by a decline in its availability as it becomes less profitable for vendors to supply a shrinking market. Should this come to pass, we all will be faced with the need to convert to 134a or whatever is its replacement. And when that happens, each region will develop an SOP based on what has worked best. In milder climates, the simplified method I and others have successfully used may be best, while elsewhere, such as south Texas, a more comprehensive replacement program may be in order. When I lived in Saudi, nothing worked to keep you cool as well as a one-way ticket on an air conditioned Pan Am 747 to New York... the cold Heinekin in my hand also helped. So where you are, or aren't, counts as much as what you do.

After all is said an done, Kip's problem is to decide what to do. My approach has always been to start cheap and spend more when it becomes necessary if this can be done without wasting scarce $$.

Good luck with this,

230/8

...I'm in Canada, where, at least in my region, we need A/C for about 1 - 2 months, if we're luckey. (LOL).
My 85 350SE's condenser was shot, so I hesitantly phoned for an estimate on conversion and replacement. (As you may know, R12 is like heroin here, you go to jail if caught importing the stuff! But I digress...)
I followed many of the threads here on conversion. In the end, it cost me $530.15 CDN (about $400.00 USD) for a new condenser and a full charge with something called 'AC-Freon R414B (59)'. So far, it's worked fine, and I thought the price quite reasonable.

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1986 560SL
2002 Toyota Camry
1993 Lexus

Man, what a blend that one is. HCFCs and Hydrocarbons:

HCFC - R414B

A blend of R-22, R-124 and R-142b with hydrocarbon R-600a (isobutane) added to improve mineral oil miscibility. This blend can be used to retrofit R-12 automotive air conditioning systems as well as stationary refrigeration systems. The pressure and system capacity match R-12 in 45F to 50F evaporators, and the discharge pressure in hot condensers is only 5 to 10 psi higher than R-12 (a benefit in automotove AC and warmer refrigeration environments). The temperature glide runs about 13F in the evaporator. The addition of isobutane to this blend significantly improves mineral oil compatibility, particularly for high viscosity oils used in auto AC.

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1986 300E 5-Speed 240k mi.

230/8,

You are absolutely correct in pointing out the many variables involved in a/c use. Climate, personal thermal needs and how you drive (city or highway) are all factors.

As an example, I recently met lizem100 in person. He has a very nice 300E and drives from Ft. Worth to Dallas every day, at least a 70 mile round trip commute. He has a simple 134 conversion and is happy with it.

I know his route and it is mostly freeway. Eric is thin and fit, so I don't think he needs to be chilled to the bone as some larger folks would need to be. So, given his particular parameters, the 134 conversion, even in the particular MB chassis that typically provides the worst conversion results works well for him.

Now, if someone who required colder cabin temp to be comfortable and drove stoplight to stoplight in Houston, I doubt that they could be at all satisfied with Erics car. It all depends on your own needs and situation. All this should be taken into account before deciding which way to go with your a/c.

Have a great day,

Larry, I can't help myself here (Friday afternoon, at work you know)...so thin Canadians really only need working window motors, but the more portly Floridians had best go with R12...
You're right, it's relative to all kinds of variables, including personal taste. This idea, if extended, will of course lead this thread into the kind of stuff found in the audio section concerning how to get the best bass out of your speakers.

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1986 560SL
2002 Toyota Camry
1993 Lexus