Air Speed-Automatic Auxiliary HVAC Control

The auxiliary blower motor circulates the air at the rear of the vehicle. The auxiliary blower motor can be controlled by either of the auxiliary HVAC controls. The primary HVAC control module located in the dash does not control the auxiliary HVAC system. If the vehicle does not have a sunroof (CF5), then the front auxiliary controls must be set to the rear position for the rear auxiliary controls to operate. The vehicle operator determines the blower motor's speed by placing a blower motor switch in a desired speed position or by selecting automatic operation. The auxiliary blower motor will only operate when the ignition is in the RUN position and an auxiliary HVAC control is set in any position other than OFF.

Power is provided to the auxiliary blower motor from the underhood junction block through the battery positive voltage circuit and IP wiring harness junction block. The auxiliary HVAC control module receives power by the ignition 3 voltage circuit through the right instrument panel junction block through the ground circuits.

When any blower speed is selected on either of the auxiliary control modules send a pulse width modulated (PWM) signal to the auxiliary blower motor speed control circuit. In manual operation, once a blower speed is selected, the auxiliary blower speed remains constant until a new speed is selected. In automatic operation, the auxiliary HVAC module will determine what auxiliary blower speed is necessary in order to maintain desired temperatures. At start-up in colder temperatures, the auxiliary blower motor will not begin operation at the same time as the primary blower motor. Warm coolant is circulated to the auxiliary heater core before the blower motor begins operating.