I've learned so much from the AC "experts" on this forum. I being a beginner in AC repair have only one thing to add to all that the experts here had to say:

Change the fuse (in the fuse box) for the condensor fan. Fuses actually do wear out eventually and then fail even if they were not subjected to excessive current. In a R134 converted system this is particularly important cause the pressure could go way too high if the fan does not kick in when it is supposed to. Small insurance to replace this fuse even on a R12 system.

Speaking of fuses make sure you have a spare glow plug fuse strip (80A ?) in your spare fuse kit. (I keep a spare set of assorted fuses in the glove box). The fuse strip is cheap but they are not available at your Pep Boys, etc car parts store so best to buy in advance.

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1972 450SL
1982 300D Turbo