A cheap way to decide whether or not you want to dive into the W124 A/C money pit is to have an A/C shop pull a vacuum on your system and see if it holds at all. If not, then it's up to you. If you can get at least 20 to 30 minutes, then go after the leak as per Steve's advice above. It still might be the evaporator, but you'll at least have made an informed decision about what and if you want to get it fixed.
1987 BMW 325
[This message has been edited by jeffsr (edited 07-15-2000).]