RADIATOR FAN MOTOR OPERATION
The cooling fan motor, located behind or in front of the radiator, is a small, direct current motor that rotates metal or plastic fan blades to pull or push air through the radiator. As this air passes over the radiator's fins and tubes, it draws heat away from them and reduces the temperature of the engine coolant.
The fan can be driven by a drive belt off of the crankshaft or it can be operated electrically. Regardless of the design used, inspect the fan blades for stress and cracks.
Electric fans are also inspected for damage and looseness. If the fan fails to turn on at the proper temperature, the problem could be the temperature sensor, the fan motor, the fan control relay, the circuit wires, or the controller. To isolate the cause of the malfunction, attempt to operate the fan by bypassing the control. On a computer-controlled system, this can be done by using a scan tool to activate the fan. If the fan operates, the problem is probably in the coolant temperature sensor.
It is also possible to check fan function by jumping the fan relay to attempt operating the fan motor. If the fan operates, the relay may be the faulty component; however, additional tests will have to be performed on the control circuit of the relay.
A jumper wire can also be used to jump battery voltage directly to the cooling fan. If the fan motor fails to operate, check for proper ground connections before faulting the motor.
To direct air flow more efficiently, many manufacturers use a shroud. Proper location of the fan within the shroud should be at least 50 percent inside the shroud. If the fan is outside the shroud, the engine may experience overheating due to hot under-hood air being drawn by the fan instead of the cooler air. If the shroud is broken, it should be repaired or replaced. Do not drive the vehicle without the shroud installed.
The fan that draws cool air across the radiator can be driven by either a belt or electricity. Rotating fans can be dangerous. Some are controlled by an automatic switch and can start unexpectedly. When working on electric fans, keep in mind that electric cooling fans should be disconnected when working around them.
When replacing a radiator fan motor, always refer to the vehicle's service manual. The following is a general guide for cooling fan replacement.
· Disconnect the negative battery terminal at the battery. This is necessary on vehicles using electric fans, but some vehicles may require the relocation of the charging system components.
· Drain the cooling system.
· Loosen or remove the hose clamps, then remove the upper and lower hoses from the radiator.
· Disconnect the transmission cooling lines and plug them off, if equipped.
· Disconnect the electric fan motor connector, if equipped.
· Remove the fasteners attaching the fan module to the radiator.
· On some vehicles equipped with air conditioning systems, it may be necessary to discharge the system. This is the case if the radiator and condenser can not be separated in the vehicle.
· Remove the upper radiator cross member or mounts.
· Disconnect and plug the air conditioning lines at the condenser, if needed.
· Remove the radiator and fan module as one unit if possible.
· Separate the fan module from the radiator.
· If required, separate the radiator from the condenser.
· Remove the old fan module.
· Install the new fan module onto the radiator.
· Reattach the fasteners attaching the fan module to the radiator.
· If equipped, connect the electric fan motor connector.
· Reinstall the radiator.
· Refill the cooling system.
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