Be sure that the wires are in the right side of the control unit. I have seen them swaped on many occasions. It usually does not hurt anything, but should be checked. You have to get the CD or the manual to check this. There is a good section on climate control in the CD.
1981 280GE SWB
ASE CERTIFIED MASTER AUTO TECHNICIAN
SERVICE MANAGER FOR 14 BAY FACILITY
MERCEDES SPECIALIST 8 YRS
PARTNER IN MERCEDESSHOP.COM