Well this is the sort of question that needs the car to hand to look at but you should check all the fuses and connections, etc. Also pull the face off of where you control your fan speed and see if those dials are working properly. If everything is fine there then I can't help you. Maybe someone else has had the same problem but I haven't. Sorry I can't be of more help.
Kind Regards
Tristan Hanwell
May 2006