I had the exact same experience two weeks back with my 90 300e. I replaced the 30 Amp fuse, it was cracked but even after fixing that I am still with out the use of the climate controlls. I started a thread not too long ago about this and I've narrowed it down to either the control unit (with a volt meter you can test for this- how is explained in my previous thread) or the resistor that lies under the blower motor. Don't want to replace both as that is expensive. I am hoping to test the relay this weekend and determine next steps. I've actually been too busy and the weather has not cooperated with working on the car. Let me know how you make out as our problems are identical.
Good luck
Mark