Blower Speed Controller

Blower speed controller is attached to the evaporator lower case. See Figure. It converts low current signals from the electronic control assembly to a high current, variable ground feed to the blower motor. Blower motor speed is variable. It is controlled by the electronic control assembly software and blend-air door actuator position. A delay function provides a gradual increase or decrease in blower motor speeds under all conditions.

A power transistor circuit is also contained in the blower motor control unit. It supplies voltage to the clutch cycling pressure switch, which supplies voltage to engage the A/C compressor clutch.