Most electric fans are mounted directly to the radiator itself and contain their own shroud for maximum cooling. Factory fans are usually bolted in using a variety of brackets for mounting, and aftermarket ones for vehicles that did not come with an electric fan use a special zip tie-like mounting system designed specifically for radiator applications. If the electric fan is mounted on the engine side of the radiator (or the back), then it is a puller fan, which means it pulls air through the grille and over the radiator core. If the fan is mounted on the grille side of the radiator (or outside), then it is a pusher fan and displaces air over the core in that manner. Puller fans are generally more efficient, but due to engine compartment room issues or engine-driven fan placement, a pusher fan may be necessary. Some vehicles utilize a dual electric fan setup for maximum air flow.
Because of the nature of an electric fan, it must use electricity in order to operate. In a vehicle application, it will make use of the 12-volt system in place in the automobile to power its motor. The fan will have at least one negative and one positive wire coming from the motor. Some fans will run backward if you reverse these, so make sure they are hooked into the correct terminals. Stock fans will run through a wiring harness and, many times, be hooked up to thermostatic controllers, while aftermarket ones are sometimes simply hooked up to a toggle switch in the passenger compartment so that the driver can decide when the fan comes on and when it turns off.
Stock electric fans are usually hooked into some sort of thermostat sender so that it turns on only when the engine reaches a certain temperature preset in the thermostat. Stock fans will also come on any time the air conditioner is run to ensure that the extra load of running the compressor doesn't unduly increase engine heat. Some aftermarket fans are available with thermostats, and some can even be programmed by the owner to turn on and shut off whenever a certain temperature is reached. If the electric fan does not come on when the air conditioner is activated, there may be a problem with the controller or the wiring, or even the fan motor itself. It is possible to bench test the fan by hooking the negative and positive wires directly to the battery for a minute to see how the fan operates. If the fan comes on and stays at a constant speed, the problem is probably in the thermostat or the wiring.
