The alternator's cooling fan is a powerful centrifugal type. It is mounted on the rotor shaft, and may be an integral part of the drive pulley or part of the rotor.
It is essential to maintain a cooling stream of air over the diodes and stator. Due to the short length of the rotor, the cooling air needs to be spiraled in. This creates a long cooling path for the air and helps maintain component temperatures within manufacturer's specifications.
To achieve this spiraling affect, the cooling fins on the plate have different openings - small and large. To get the maximum cooling affect, the alternator fan must be driven in the correct direction. Refer to the manufacturer's specifications for this.
The fan at the front of these alternators is an exhaust fan. The fan draws air in through the opening at the back of the alternator, where the air will pass through cooling fins at the rectifier heat sink. And the air will be drawn through the stationary “stator windings”, where the air will also have a cooling effect. As usual with moving air through passages, the same fan efficiency will suck more air than the fan could blow through. That’s why the fan at the front is an exhaust fan.
It must be noted about alternator cooling, the greater the AMP rating of the alternator the more heat it can generate.
