Thank you! I'm glad that my expertise was helpfull.
Anyway, as I mentioned in my previous post, I TOUGHT that I figured out what is wrong. In fact the problem was a bit different.... After checking again the fuses behind the glowe compartment (f7, f20, f22 and f75) I was surprised that none of them was in fact blown. Before I go on with the article, I must say at risk of sounding silly, that like many other electrical systems, my car allso must have a daemon within the wires.... Last summer, a day before taking a 2 weeks vacation in Germany ( max. speeds under 210 km/h in Germany, alltough my wife did not even noticed that while reading a book...), the Aircon stopped blowing cold air. The solution was quickly found by our workshop electrician: the f22 fuse blown. At that time the aux fan was the old one wich recently died. For the next year and until the other weekend when again I had to take a 2 days vacation, the A/C system performed fairly. Half an hour before having to leave the city with my family, the f22 fuse blew. That is why I suspect the car has its moods...
Ok, we took the trip, went back and after 2-3 days the aux fan died for good (fuse blown again). After a few calls, I got a used aux fan for about 45€. Unfortunately in the process of replacing it with my old fan, one of the wires coming out of the 2nd stage resistor got broken and I had to use the resistor out of my old fan assy. Funny thing is that out of two identical resistors I chose the one that (did not know till yesterday) was broken or burned or dead. Before deciding to jump it with an 2.5mm wire I took out the socket out of the thermoswitch and fooled the car into believing that the coolant had 94 deg by jumping ground with 2nd stage line, respectively 104 deg by jumping the GND with the 3rd stage line using a 10 cm long wire. The only reaction was that third stage fan speed was working since it goes directly to the fan motor and does not go through the two resistors. Since those (resistors) are serially connected, the logical conclusion was that the resistor next to the fan motor is faulty. That was the case in reality when I measured its resistance. Soon I will again strip the car off its bumper, headlights, air guides and manny other parts in order to replace the resistor. After that I expect no other difficultyes and all three stages of the aux fan to run as intended by the Bavarian manufacturer...