The 2007 Toyota Yaris blower motor system consists of following components: blower motor, heater control (blower switch), heater, battery, alternator, relay and gauge, blower resistor and air conditioning amplifier. When the heater control (blower switch) is set to position 1 or higher, the contact of the HTR relay is closed, current flows to the blower motor, and the blower motor operates. The blower motor speed can be changed by exchanging the ground and the blower resistor circuit with the heater control (blower switch). Below diagram shows the 2007 Toyota Yaris Blower Motor Circuit and Wiring Diagram. (click image to enlarge).