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.

Keep in mind:

• The cooling fan can run even with the ignition off. Use caution when working in and around the cooling fan to prevent personal injury.
• Some vehicles are equipped with two cooling fans, with separate cooling fan relays controlling each one.

How it's done:

• The Cooling Fan Relay is verified that it needs to be replaced. The main access relay panel is open to access the cooling fan relay.
• The defective Cooling Fan Relay is removed from the relay box by pulling straight up and out of the connection.
• The connection is checked for any damage or overheating. The new Cooling Fan Relay is installed by lining up the pins and pressing it into the connection.
• The Cooling Fan Relay is tested for operation by running the engine or turning on the A/C.
• The vehicle is tested for proper operation of the Cooling Fan during a road test.

Our recommendation:

The cooling fan relay is meant to last indefinitely, but as with all electrical components, it can fail prematurely. There are no preventative measures you can take against its failure. If your engine temperature rises into the red zone, or if the cooling fan won’t quit operating, have one of our expert technicians diagnose the problem and replace the cooling fan relay if required.

What common symptoms indicate you may need to replace the Cooling Fan Relay?

• Engine temperature runs higher than normal or overheats
• Air-conditioning does not function
• Cooling fan continues to run indefinitely

How important is this service?

The electric cooling fan plays an important role to control engine temperature. In a situation where the cooling fan will not turn on, overheating and engine damage can occur. If the cooling fan runs continuously, the fan motor can burn out or electrical drain can deplete your battery. If the cooling fan relay is faulty, have it replaced as soon as possible to prevent additional, expensive repairs.