Circuit Description

The Heater Blower Circuit is made up of the following components.

1. Low Speed [1][2]Blower Motor Relay
2. High Speed Blower Motor Relay
3. Blower Motor Resistors
4. Blower Motor Switch
5. Blower Motor

The Blower Motor has 4 speeds when the Blower Motor Switch is in the "LO" position and the Mode Selector Switch is closed and ground is applied to the three resistor element within the Blower Motor Resistor. The Blower Motor then runs at Low speed. When the Blower Motor Switch is in the "MED" position, a ground path is created via the Mode Selector Switch, Blower Motor Switch and two of the three resistor elements within the Blower Motor Resistor. The Blower Motor then runs at "MED" speed. When the Blower Motor Switch is in the "HI 1" position, the High Speed Blower Motor Relay coil is energized through the Blower Motor Switch. The relay contacts close and ground is applied through the relay contacts to the Blower Motor Resistor. The Blower Motor receives a ground signal through one resistor element within the Blower Motor Resistor. The Blower Motor then runs at "HI 1" speed. When the Blower Motor Switch is in the "HI 2" position, ground is applied directly to the Blower Motor, bypassing the Blower Motor Resistor. The Blower runs at "HI 2" speed.

With the Ignition Switch in "RUN", the Low Speed [1][2]Blower Motor Relay receives battery voltage from the ENGINE Fuse. The relay is energized by receiving a ground through the Starter Motor. Voltage from the HEATER Fuse is then applied to the Blower Motor through the contacts of Low Speed Blower Motor Relay and the BLOWER MOTOR Fuse. When the Ignition Switch is in the "START" position, battery voltage is applied to the ground side of Low Speed Blower Motor Relay. This de-energizes the relay forcing the Blower Motor to stop during engine cranking.