A basic vehicle cooling system consists of a radiator, water pump, thermostat, electric or engine-driven cooling fan, and hoses. Electric cooling fans are common on today's vehicles due to engine compartment space limitations or engine layout. Electric cooling fans operate in either a pusher or a puller capacity. A pusher type fan is typically mounted on the front of the radiator assembly and forces air through the radiator, whereas a puller type fan is mounted on the engine side of the radiator and draws air through the grill and radiator assembly. Vehicles that utilize a transversely-mounted engine will always be equipped with at least 1 electric cooling fan (most having 2), because none of the engine pulleys are in-line with the radiator air-flow.
There are generally 2 types of electric cooling fans: primary cooling fans and secondary cooling fans. Primary cooling fans are typically of the puller style. Vehicles that do not incorporate an engine-driven mechanical cooling fan will utilize a primary cooling fan. The secondary cooling fan, also known as an air conditioning condenser fan or auxiliary cooling fan by certain manufacturers, could be of either a pusher or a puller style. Vehicles equipped with air conditioning will either utilize the radiator cooling fan or a separate fan as the air conditioning condenser cooling fan (which performs the same function as an auxiliary cooling fan on vehicles with a primary mechanical fan). The engine control computer that receives inputs from various sensors in the engine compartment commonly controls electric cooling fans. The engine control computer receives inputs from the engine coolant temperature sensors and air conditioning system pressure switches, then actuates the necessary cooling fan relays to engage the applicable cooling fan for the condition. On models equipped with only 1 electric primary cooling fan, the fan can operate at 2 speeds: low speed and high speed. The low speed condition is enabled when the engine begins to heat up or when the air conditioning is engaged. As the engine demands more cooling, the cooling fan will be stepped-up to high speed.