problems with a/c switch?!?!

dear forumers

firstly, i'm a newbie here. greetings....

I own a z3 2.0 y2000 and have been experiencing intermittent problems with my air conditioning unit.

Problem:
fan speed 0 to 3 does not work but 4 is ok.

Any of you guys can advice what seems to be the problem?

rgds

FInal stage aka blower resistor needs replacing. Cost around 50$ at a dealer.