Air heating and cooling systems in cars (and in homes and other buildings) most commonly rely on forced air. Forced air is passed through heating or cooling elements and circulated to the desired locations. Blower motors provide that air movement.
A blower motor is a term that actually describes a combined unit--an electrical motor and a fan. Most often, a centrifugal fan, which looks like a 6- to 10-inch hamster cage, is used. These fans--mounted in "housings"--are used to force hot or cold air through ducting and vents.
Blower motors for automobiles are located within a housing on the firewall (the structure that separates the interior cabin of a car from the engine bay). They are almost always positioned on the passenger side, opposite the steering and braking components. They draw in outside air, pass it through heating and cooling elements, and force it through a plenum and ducts leading to various interior vents.
Similar to automotive blower motors, Residential and commercial blower motors are used to circulate conditioned air (whether heated or cooled) from a furnace or cooling system throughout a home or commercial building. These units are designed on much larger scales than automotive applications. Since they are required to move far more air, they may be many times larger than automotive blower motors--say, 60 to 120 inches across rather than 6 to 10 inches across.
