On the left side of the engine compartment (drivers side), toward the front, there is a drier bottle. It is located behind the headlamp. It has a switch with that is red with wires coming out. IF you bridge them while the car is running, the fan should come on. If not, you have to figure out why.
Start at the resistor that is in the same area. IT is ceramic and tan in color. Check for power in and out. If You have power in and not out, bridge the two wires.
ASE CERTIFIED MASTER AUTO TECHNICIAN
MERCEDES SPECIALIST 11 YRS