HVAC System - Manual

AUXILIARY BLOWER CONTROLS (HEATER WITHOUT A/C)
CKT 341 (BRN) supplies battery voltage to relay coil cavity 5 of each of the 3 auxiliary blower relays when the ignition switch is in the RUN position. CKT 542 (RED) supplies battery voltage to cavity 1 of each of the 3 auxiliary blower relays when the ignition switch is in the RUN position. The relay coils are not grounded and the relays remain de-energized when the auxiliary heater control switch is in the OFF position. The auxiliary blower motor is supplied no voltage and the relay contacts remain open.

A ground path is provided for the auxiliary low blower relay coil through CKT 1926 (DK BLU) to the control switch when the ignition switch is in the RUN position, and the auxiliary heater control switch is in the LO position. A ground path is then provided through CKT 150 (BLK) to ground G200. The relay coil energizes and the relay contacts close. CKT 1176 (YEL) applies battery voltage to the auxiliary blower resistor. CKT 1172 (YEL) carries a current through 2 resistors and to the auxiliary blower motor. The motor operates at the slowest speed.

The auxiliary medium blower relay is energized when the auxiliary heater control switch is in the MED position. The current flows to the motor through 1 resistor and the motor operates at an intermediate speed. The auxiliary high blower relay is energized when the auxiliary heater control switch is in the HI position. The current bypasses both resistors and the motor operates at the highest speed.

The auxiliary heater control switch provides an illumination lamp in order to facilitate switch operations. The lamp is powered by the instrument panel dimming system.

The auxiliary blower motor is controlled by either of 2 auxiliary blower switches when the optional auxiliary heating and air conditioning is provided. Both switches are located in the overhead modules. 1 switch is located in the instrument panel. The other switch is located in the center of the vehicle. The auxiliary blower motor operates from the auxiliary blower switch. The auxiliary switch is located at the front auxiliary HVAC control module and is in the REAR position. Refer to HVAC Air Delivery Circuit Description for a description of the control priorities for the ventilation modes. HVAC Air Delivery Circuit Description

CKT 341 (BRN) supplies voltage to relays coil cavity 5 of each of the three auxiliary blower relays when the ignition switch is in the RUN position.

CKT 542 (RED) supplies battery voltage to contact cavity 1 of each of the 3 auxiliary blower relays when the ignition switch is in the RUN position. No ground path is provided for the relay coils when the auxiliary blower switch located at the front auxiliary HVAC control module is in the OFF position. The relays remain de-energized. The relay contacts remain open. No voltage is supplied to the auxiliary blower motor.

A ground path is provided for the auxiliary low blower relay through CKT 1925 (DK BLU) to the front blower switch when the ignition switch is in the RUN position, and the blower switch (located at the front module) is in the LO position. A ground path is provided through CKT 150 (BLK) to ground G400. The relay coil energizes. The relay contacts close. The relay coil applies battery voltage to the auxiliary blower resistor through CKT 1176 (YEL). The current flows through the 2 resistors and to the auxiliary blower motor through CKT 1172 (YEL). The motor operates at the slowest speed.

The ground path is different when the auxiliary blower switch at the front HVAC control module is in the REAR position. The ground path is different when the auxiliary blower switch at the auxiliary HVAC control module is in the LO position. The ground path travels through CKT 1925 (DK BLU) to the auxiliary HVAC control module. CKT 77 (DK BLU) continues the ground path to the auxiliary and HVAC control logic module. CKT 77 (ORN) continues the ground path to the front auxiliary HVAC control module and continues to ground G400.

The auxiliary medium blower relay is energized when the auxiliary blower switch is in the MED position. The current flows to the motor through one resistor. The motor operates at an intermediate speed. The auxiliary high blower relay is energized when the auxiliary blower switch is in the HI position. The current bypasses both resistors. The motor operates at the highest speed.

In order to facilitate switch operations, an illumination lamp is provided at each HVAC control module. The lamps are powered by the instrument panel dimming system.

The circuit operation for the optional auxiliary system is similar to that for the optional auxiliary HVAC option.