High Blower Speed
WARNING: This page is about a different car, the 2003 Chevrolet Corvette. However, it is still accessible from the selected car via links, so may be relevant.
When the High (5) blower speed is selected, the HVAC control module applies voltage to the blower motor resistor assembly relay through the high blower motor control circuit. The voltage energizes the relay, causing the blower motor to be connected to the battery positive voltage circuit. The blower motor resistor assembly provides a ground path for the blower motor.