I have a 97 e320, when i turn on the ac, the fan blows only at one speed. Whether its at the lowest setting or the highest setting. It actually blows just alittle bit harder at higher settings, but very little, almost not enough to notice unless u really pay attention. Does anyone know what the problem is. I'm guess its the heater/ac controller. But is there a sensor that regulates the speed, or could it be my motor. Any suggestions.