Hi, my name isXXXXX a 2003 W211 chassis that procedure does not work. The procedure only applies to the W210 models. The only way to reset the climate control unit on your car is to have the car connected to the Mercedes Star Diagnosis tester to erase the fault codes. The EC light will come on if your system is low on refrigerant or if there is a fault with one of the climate control sensors. Usually the system will require a recharge to repair this malfunction but the fault codes will point to the specific problem.
My mechanic does not have a Mercedes Star Diagnosis tester just a code tester. Should I take the car to a certified Mercedes dealer?
Yes you will need to take the car to a Mercedes specialist. If your mechanic can evacuate and recharge the a/c system you might be able to get the EC light to reset by adding refrigerant if the system is low.