High Blower Speed
WARNING: This page is about a different car, the 2003 GMC Sonoma, 2003 GMC Jimmy, 2003 Chevrolet S10 Pickup, and 2003 Chevrolet Blazer. However, it is still accessible from the selected car via links, so may be relevant.
When the High blower (4) speed is selected, the HVAC control assembly applies voltage to the blower motor relay through a portion of the high blower motor control circuit. The blower switch will direct the voltage through the high blower motor control circuit. When the load side of the relay coil is energized, the blower motor is connected directly to battery voltage through the blower motor supply voltage circuit. The ground circuit provides a ground path for the blower motor.