Being a DIYer myself, I still have all the leak testing, evacuating, and charging done by my local A/C shop. Having a 100% DIY system would not be worth the effort in my opinion. Even if I did have the education and licensing (for refrigerant purchasing) to properly service my own systems, I am still better off paying the experts to do it. As many 'Benz A/C systems as I have done, it still would not be worth the expense and effort to become my own A/C "shop". As far as the refrigerants available (excluding R12 & R134a), you (Paul) have done a great job informing us what the pros and cons are for each one. The main thing I would be concerned about with refrigerants other than the normal R12 & 134a, is contamination. You explained it quite well, and I agree:
"Regardless of the path a DIYer takes, ensure that the system is clearly labelled to prevent the inadvertent contamination of commercial recovery systems in the future that may not test for the refrigerant in the system. Be a good neighbor."
As far as I am concerned, that is the most important rule when using refrigerants other than the norm. There are shops that do not have a refrigerant analyzer, so an unlabeled contaminated system could cause what could be called a "virus" to spread throughout the serviced vehicles from said shop/s. I for one will stick with the standard R12 & 134a refrigerants, as long as they are still available. No "designer" refrigerants for me (or my local A/C shop).......Rich

I bought some R12 on ebay: 3 tselve oz cans of DuPont and 1 can of oil. I signed a statement saying that the person the stuff would be used by is a licensed AC tech. That was good enough and in the mail it came.

Turns out that none of the shops around here have the fittings to get it in the car (12 oz DuPont cans). I presume that this also means also don't have the means to evacuate the system as well.

And then it dawned on me. Can I have a shop in Canada properly evacuate and then recharge the system with R12?

canada will draw and quarter you if your bring R12 into their country...

Thanks for the good advice! After posting this here I did some poking around on-line to find that R12 is illegal in Canada and Wisconsin.

I'm very basic. I use R-12 in my own R-12 systems, and I am still licensed to purchase it. It is plentiful and cheap on E-Bay. I do perform retrofits and find that R-134, when properly installed, gives good performance in orifice tube systems, but not as good in a TXV system, unless you pair it with a proprietary R134(a) TXV, and, for some vehicles, they do not make them.

Envirosafe gets good reviews and it might be good, but I am yet to test it. Nice, creative and informative write up...

R12 is the refrigerant of choice for any pre '85 Mercedes. R134 will work OK in some late MY 84 W126 cars and '85 W126s although, the R4 compressor is a power hog when using R134.
There is an inexpensive direct bolt in condenser available for the W126 300SD that offfers good performance. It is typical china construction therefore I have little faith in it's longevity with the diesel engine vibrating on the compressor end of the hose.

In the W116 R134 seems to work OK in some cars which I find odd as this chassis has a poor condenser. Out of interest we just charged up a W116 with R152 after recovering the R134 from a working system. The operating pressures of R152 are closer to R12 so I expect the compressor life to be extended plus a savings in HP. Feedback so far shows it is cooling slightly better than R134. We did nothing other than remove the R134, change the dryer and pull a deep vacuum for about one hour.
I have my doubts it will be sufficient when we have the next 100f ambient day.

Enviro-Safe ES12 looks interesting and I have plans to try it in my W126 in a few days.
It currently is running R134 with the upgraded condenser and small water pump pulleys.
Vent temps on average are 48-52f, blower on "hi" an an ambient temp of around 95-98f which I can live with.

I may try R152 for a few days before trying ES12 and report back.

Please do!

At $12 for three cans why not...

I hope that this thread is still active. I have a 1994 mercedes e320 which has a bad evaporator. It is placed in a position which requires at least 17 hours just to get at it and replace it; then probably another 17 hours to put it back together. So, I am wondering if there is some way to bypass it and install an evaporator under the hood and connecting it into the ac lines? Or am I just having a flight of fantacy and if I want ac I need to do the job?

The purpose of an evaporator is to provide a refrigerant to air interface - in other words a "radiator" with cold refrigerant that hot air moves across and becomes cooler. If you want to cool the engine compartment, your idea to place the evaporator there would do a great job. If your goal is to cool the passenger compartment you have no choice but to replace the defective evaporator.

All threads remain active, so by definition this thread is active, however it would be best to start a new thread describing your issue and gaining feedback on that specifically.

there is a new refrigerant leak sealant, that is compatible with oils, and compressors, and does not react to moisture or air to form the seal... I've tried it in my own truck, and a few of my customer's equipment, and so far... it seems to be VERY good stuff.

it could be the solution for 134 seepage through the non barrier hoses, and a solution for leaking "impossible to get to" evaporators...

You want to let us know what this sealant is, or do you just want to keep it a deep dark secret and all of us wondering....:)

Um, I just bought another tube of it, I'll go check the name... leak freeze I think...

yup. leak freeze. NOT THE MAGIC FROST version. just the standard.
around 40 bucks online...
http://www.airstarsolutions.com/Pages/ACLeakFreeze.aspx
http://www.rjnunnally.com/ac-leak-freeze-with-magic-frost-review/

I have been using the propane/iso butane mix for a couple years now and it is working great. I think next I will try R152a. This SAE paper shows it to be superior to R134a

http://www.sae.org/events/aars/presentations/2008/manhoekim.pdf