It is my understanding that you can reach the potentiometer after removing the instrument cluster. Your mechanic may need short/stuby screw driver but according to the Mercedes Repair CD it is possbile.

Haasman

__________________
'03 E320 Wagon-Sold
'95 E320 Wagon-Went to Ex
'93 190E 2.6-Wrecked
'91 300E-Went to Ex
'65 911 Coupe (#302580)