Has anyone experienced a problem with the heater output in their Z3? I have to turn the control knob almost all the way to maximum to get any significant heat output. The heater itself seems to work well, but for some unknown reason, the control knob doesn't activate the heat until it's turned to the maximum heat setting. I took the car to my local dealer and they said that there wasn't anything that they could do about it. Is this normal? If not, what can be done to correct this? Thanks for your help.