Slow down. I don't think you can infer that because your blower fan does not work at low speeds that the evaporator is the culprit.

For the blower problem, I'd suspect your pushbutton assembly/controller. Once that is sorted out (fan works correctly at all speeds and the heat works via climate control) you can begin to diagnose the AC problem.

Your lack of AC may indeed be due to a leaking evap core but there are many other things to check first..... I'm sure others will chime in to talk you through the AC diagnosis - ONCE YOU HAVE GOTTEN THE FAN TO WORK CORRECTLY.

Chris Blanchard
1992 300D 2.5 Turbo 151k