Good call Larry, I might also inquire if you are trying to adjust the temp wheel. There will be little change in blower speed if you leave the setting at "Min".
In auto blower position, fan speed is a function of the deviation between set temp and the actual sensor readings. If any sensor is vastly skewed the deviation won't change much as real temps change (all changes are relatively small in comparison to a really skewed sensor). Lack of airflow can be one of the greatest problems as the heat of the roof gives a false inside temp reading.
Bosch Master, ASE Master, L1
33 years MB technician