Just got a 92 740 wagon. The A/C was filled and worked fine for a week. R12 pressure is down to 20 psi. I suspect a leak, and since the compressor is soaked with oil, that it is leaking at the shaft seal. I have another compressor from my old 85 740, which feels OK. Its A/C did not work but it had a rusted out pipe. I plan to swap the compressor and try it again. If it fails, then I would try and replace the first A/C seal. Is this easy to do? Anyone done it?

If it's down to replacing the seal, get a new compressor ( you can get a new sanden 709 from www.nostalgicairparts.com, very reasonably, it's a nice upgrade over the factory compressor )
the tools to replace the seal are expensive ( clutch puller installer, shaft seal tool, shaft seal protector )and results for a first timer are generally questionable.
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-------Robert, '93 940t, '90 240 wagon, '84 240 diesel (she's sick) , '80 245 diesel, '86 740 GLE turbo diesel, '82 Mercedes 300SD for sale

Check out "centuryautoac.com". Very helpful. They can rebuild compressors and ac lines. Very good prices on o-ring kits and tools.

swap and try is expensive gamble with r12. new compressors are less.

Anybody know what a complete refill for R-12 is running these days?

That's for sure! New compressor can be had for $180. Seals run $15 to $20+ depending on which compressor is on car, there are different ones, plus the tools to install them are not cheap. My set cost over $75 for this type compressor. Correct seal installation on these compressors is not easy WITH the special tools.
New compressor, IMHO, definitly the most cost effective way around problem. As long as I can get new unit for under $200 shipped to my door, I will never replace another Diesel-Kiki, Xexel, or seltec compressor seal. I have ruined more than one of those expensive seals or had old compressor crap out after putting in new seal. Don't waste time using old parts if you want it to work and not have to do same job over again. Good luck,rcs

My '89 740GL needs regassing every couple of years, It has a retrofit kit
to convert it to R134a gas. The compressor is a sanden which does its job faultlessly. but there is some doubt about the sealing ability of the system.I've had it checked by my mechanic and he's put the test guages on it and it has come up trumps.

Another friend of mine who owns an '86 model has had no problems with hers and it has held its gas for over ten years now and goes much colder than mine when gassed but hers is an R12 system so I dont know whats going on with that!

I've been told that the new systems are much more eficient and much more colder than than the previous systems, Is this true or or is this "Clap Trap" as I cant test it with my system.

Maybe that the R134a system is not as good as the previous R12 systems on sealing the refridgeration side of things in the A/C system.

If anbody knows the answers to any of these questions, drop us a line on the brickboard site.