Ockman made a good point about R134 and it's limited capacity, however, if you have already changed to R134 and you want to change back, proceed with caution. You don't want R134 to mix with R12 in any way, don't even get them close to each other. If you decide to switch back, which I wouldn't do at all, make sure you get the compressor completely clear of the old oil. Then completely disconnect everything in the a/c system and flush "thoroughly".
I don't think that the aux. fan not working would have a drastic effect on cooling ability, the main reason for its existence is to bring down high side pressure when it gets too high. This keeps from blowing something out.
If your system is still R12, I expect that it is inadequately charged, but don't assume so and add R12 without checking everything first.
'84 Euro 240D, 523K miles
'88 300E 5 Speed
'81 300D Daughter's Car
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