Blower Motor Control

Operation of the blower motor is controlled by the automatic temperature control (ATC) module. The automatic temperature control (ATC) module monitors a feedback voltage from the blower motor control module. In response to the feedback voltage, the automatic temperature control (ATC) module provides a drive signal back to the blower motor control module which is used to regulate the voltage flow across the blower motor and hence regulate blower speed. The blower motor is provided with a battery voltage feed from the blower motor relay, which is located within the auxiliary junction box.

When the air conditioning (A/C) system is in automatic mode, the automatic temperature control (ATC) module determines the blower speed required from its 'comfort' algorithm. When the air conditioning (A/C) system is in manual mode, the automatic temperature control (ATC) module operates the blower at the speed selected using either the rotary control switch or the '+/-' soft buttons on the TSD.

The automatic temperature control (ATC) module also controls blower motor speed to compensate for the ram effect on intake air produced by forward movement of the vehicle. As vehicle speed, and consequently the ram effect increases, blower motor speed is reduced.