To test the mechanical cooling fan, hand-rock the fan to test excessive bearing play, and to test that it moves freely turn the fan blades by hand with the engine cold. Check the presence or absence of fluid leakage of the clutch assembly and change it when required. When the engine is warmed up, with the ignition turned off, the engine needs to be checked to ensure there is no drag when turning the fan by hand; when the fan turns easily, the fan clutch must be changed. In the case of the auxiliary electric cooling fan, the failure to work occurs, then examine the heating and cooling system fuses in the engine compartment and the passenger compartment. In the event that the fuses are intact, test the fan motor by applying battery power to it; change the motor in case it does not work. When the motor is working reconnect the fan connector, and check the cooling fan thermo switch on the bottom of the radiator or in the lower radiator hose, depending on the type of engine. Connect the relevant terminals in the switch to check whether it works; when the fan starts running, the circuit is working properly and this means that the thermo switch is faulty. When the cooling fan is not functioning when bypassed, verify the cooling fan relays in the instrument panel fuse/relay box. In case the relays are functional, the problem can be in the wiring harness, fan control module, or high-pressure switch, which requires the verification of the occurrence of open or short circuits. To replace the mechanical cooling fan, loosen the fan retaining nut with a spanner wrench, remove the fan/clutch unit out of the engine compartment, examine the fan blades to determine whether they are damaged or not and unscrew the fan to the clutch when necessary. Installation is done in reverse order and the mounting nuts are tightened. In the case of the auxiliary electric cooling fan, elevate the vehicle, lift the lower engine cover, unscrew the electrical connectors, empty the cooling system and strip the radiator. Dislodge the air intake duct and loosen the auxiliary cooling fan mounting nuts and carefully remove the fan, particularly when equipped with air conditioning, so as to not to tear the condenser. Should the fan blades or motor be damaged then the fan blade can be removed off the motor and then installed again in the reverse order.