A/C conversion 1982 380SL

'82 300SD just done last month. About $300 (including dye and evac and all the other little things that get tacked on). Just charging the old system with freon would have been about $250.

Don't do it. New freon is much less efficient in heat transfer and the SL's system is already marginal. It short, you won't get enough cold air to do yourself any good in hot weather. A good, tight R12 system is far superior in cold air output.

Be sure the mechanic replaces the freon pressure switches. I suspect many people who didn't get adequate cooling after conversion might be trying to run R-134 within R-12 vapor pressures--not a very efficient way to go. Also check all compressor seals and the low side suction hose for leaks. However if your system isn't leaking, then I'd just add R-12 until it becomes necessary to convert.

The "New Freon" is not freon at all but a refrigerant called 134A. It is sold at all Wall Mart stores! Converting requires the replacing of the receiver/dryer, standard procedure. Any good service station can do the conversion. Find one who injects fluorescein into the system. It will reveal the exact source of a leak when exposed to UV light. To convert is not voodoo, but removing the contaminants from the system, installing the 134A, changing the screw-on caps for both ends with ones that indicate the new refrigerant. It will cost less if you source the new receiver/dryer from Rusty at 800-741-5252. He discounts all MB parts and is the official parts supplier for mbz.org. My conversion costs under $100. P.