HVAC Blower Controls Circuit Description

The front heater and Air Conditioning (A/C) functions are controlled by the heater and A/C control module which include the following components:
^ The mode switch
^ The blower switch
^ The temperature control motor

The battery voltage is provided to the controls by the HTR-A/C Fuse (Fuse 12). The high speed blower voltage is provided by the FRONT HVAC Fuse. When the blower relay is energized, the voltage is provided directly to the blower motor. The blower relay is located in the blower motor resistor and relay pack.

The blower speed is controlled by the blower switch in conjunction with the mode switch. Voltage from CKT 141 (BRN) is passed through the mode switch. The voltage is then passed on to the blower switch for all of the mode settings except OFF. The FRONT HVAC Fuse and CKT 340 (ORN) provides the battery voltage to the blower motor resistor and relay pack when the blower switch is in the HIGH position. CKT 350 (BLK) cavity C provides a ground for the following components:
^ The coil of the blower high speed relay
^ The front blower motor

When the blower high speed relay is energized, the circuit to the front blower motor is completed. The energized blower high speed replay bypasses the resistor pack. The energized blower high speed relay will operate the blower motor at high speed.

Increasing the resistance limits the current to the blower motor. Limiting the current results in slower blower motor speeds.

A current path is provided through the following components when the M2 setting is selected:
^ Cavity F of the blower motor resistor and relay pack
^ The selected resistor
^ The closed contact of the high speed blower relay
^ The front blower motor

The circuit puts 1 resistor in the circuit.

Place the fan switch in the M1 position in order to attain a lower speed.

The lower speed provides a current path through the switch to CKT 63 (TAN) cavity D of the blower motor resistor and relay pack. The current passes 2 resistors in the circuit. The 2 resistors reduce the current flow to the front blower motor. The reduced current flow reduces the blower motor speed.

Place the 3 resistors in the circuit in order to accomplish the slowest blower speed. The 3 resistors are placed in the circuit when the LOW setting is selected from the fan switch. The current flows through CKT 60 (YEL) cavity E of the blower motor resistor and relay pack through the following components:
^ The selected resistors
^ The closed contacts of the high speed blower relay
^ The front blower motor

3 resistors are placed in the circuit. The 3 resistors reduce the current flow to the front blower motor. The reduced current flow reduces the blower motor speed.