Mercedes-Benz S420 Cooling Fan Relay Replacement at your home or office.

What is the Cooling Fan Relay all about?

Modern vehicles employ electric cooling fans to draw air into the engine compartment, through the radiator, and into the air conditioning condenser. This action removes heat from the coolant in the radiator and pulls heat from the refrigerant in the air conditioning condenser. The electric cooling fan is an electric motor with fan blades attached to it. It turns on when the powertrain control module receives a signal that the temperature of the engine or air conditioning warrants the extra flow of air.

The powertrain control module then sends a signal for the cooling fan relay to supply power to the cooling fan. The fan motor relay performs the action of a switch, sending 12-volt power to the cooling fan and initiating its operation. Once the engine temperature drops below the threshold programmed into the powertrain control module, the cooling fan turns off. In some makes and models, the cooling fan can continue running after the engine has been shut off, or it can turn on while the ignition is off. If the cooling fan relay is faulty, the cooling fan can continue to run unnecessarily, even when the ignition is off and the engine is cold. Conversely, the cooling fan may not run at all causing the engine to overheat. Since the cooling fan plays a factor in air conditioning performance, your air conditioning may not blow cold air.