Blower Fan Speed/ no low speed
 

Hi guys I have an 89 560sel. Im haveing trouble with the blower speed. When I select LOW I get low fan, When I select HIGH I get high fan. But on the AUTO setting I only get MEDIUM to HIGH fan speed,no low. It will only reduce fan speed to med and will not go any lower. I removed the sensor from the over head light fixture and blew out a little bit of dust and fuzz. I then check to tubing going down to the asperator motor, that seemed to be fine and the asperator motor is running and seems to be fine also. A guy at a MB shop told me to check if it would hold a peice of paper up by the sensor and it did. Anybody have any thoughts or tips to figure this thing out. Thanks Tom