The radiator fan is electrical and controlled by the electrical engine control system. When the temperature of the coolant or engine compartment reaches the appropriate level, the system will turn on automatically.
After the engine stops, the engine fan continues to run for a while (about 10 min) to completely cool the engine. Only when the engine has cooled down does the fan stop working. But the temperature in the engine compartment can rise through the ambient temperature (under the sun or through heat). Then the fan can start working again. Therefore, when working on the engine, you must be very careful not to get injured or damaged!
If the coolant has reached the temperature at which the radiator fan should operate, but does not, the fuse should be checked and replaced if necessary. If replacing the fuse does not help, contact an authorized service station.
The fan speed is independent of the motor speed. Downshifting does not improve the cooling effect of the fan; thus, as long as the engine is running properly and the top speed does not cause a significant reduction, there is no need to downshift. Replacing the radiator fan is described Here.