1982 Mercedes 300SD turbo 5 cyl diesel mileage: 92,000. I have just purchased this car and I had heard the air conditioner's on these cars are not the greatest! As a matter of fact, I do see an awful lot of these cars driving around with the windows open in the summer. I live in Florida and I can't imagine these other drivers 'just like fresh air'. I had the Freon 'topped off', it didn't require much (a mere 2+ ounces) and it does not seem to have helped. The best I can figure, from asking questions of local mechanics, is the evaporator is simply 'too small'. The air conditioner barely cools, do I have to live with this or are there some suggestions you can make to improve the cooling capabilities?
The alternative to making the air-conditioning system "bigger" would be to better insulate the passenger compartment from the heat of the engine. Adding more insulation on the firewall and under the floor mats will help. If legal in your area, tinted windows will also help.