Abstract: A heating and air conditioning system for a motor vehicle includes a plenum supplied with air by each of a pair of variable speed blowers. A set of heating and air conditioning ducts extend from the plenum to the drivers side of the vehicle, and another set of heating and air conditioning ducts extend from the plenum to the passengers side of the vehicle. Accordingly, both the driver and the passenger can control the blower supplying air to the ducts on the corresponding side of the vehicle. A defrosting duct extends from the plenum to supply defrosting air to the windshield of the vehicle. One of the blowers normally supplies air to the defrosting duct, but the volume and velocity of air may be "boosted" by optional use of the other blower.