Air Speed-Manual Auxiliary HVAC Control

The auxiliary blower motor circulates the air at the rear of the vehicle. The vehicle operator determines the auxiliary blower motor's speed by placing the blower motor switch in a desired speed position. The auxiliary blower motor switch controls the auxiliary blower motor speed. Three relay blower motor speed control circuits enable one of three relays to provide power to the blower motor. The blower motor switch grounds the selected relay. Each relay's control and load power is provided by the ignition and battery positive voltage circuits. Both the low and medium speed relays connect to the auxiliary blower motor through a resistor assembly. The resistor assembly creates a voltage divider circuit with the auxiliary blower motor to select the auxiliary blower motor speed. The high speed relay is connected directly to the auxiliary blower motor. The primary HVAC control module located in the dash does not control the auxiliary HVAC system.