Control Module HVAC: Description and Operation

VARIABLE BLOWER CONTROLLER/HIGH BLOWER RELAY

The function of the solid state variable blower controller/high blower relay (VBC) is to convert signals from the ATC control module to a high current, variable ground feed to the blower motor. Blower motor speed is infinitely variable and is controlled by the ATC control module software. A delay function provides a gradual increase or decrease in blower motor speed under all conditions. When the ATC control module signals the VBC for maximum blower speed, a relay bypasses the solid state control and provides a direct path to ground for the blower motor.