Front Blower Motor - Heater Without A/C

The front Blower Motor controls operate by supplying voltage to the motor through switch contacts. Battery voltage is available from HTR-A/C Fuse 12 when the Ignition Switch is in Run to the Heater and A/C Controller through the BRN (141) wire. This voltage is available to the Blower Motor Switch in the Heater and A/C Controller when the Heater and A/C Controller's Mode Switch is not in OFF. This power is provided for operation of the front Blower Motor at low and medium speeds only. This power is also used to operate the Blower Motor Relay located in the Blower Motor Resistor/Relay. The relay is energized to operate the Blower Motor in HI speed. Battery voltage is supplied at all times from the HVAC Maxi Fuse to the Blower Motor Resistor/Relay through the RED (542) wire. This voltage is supplied for operation of the front Blower Motor at high speed.

With the Blower Motor Switch in the LO position, voltage is applied from the switch contacts through the YEL (60) wire to the Blower Motor Resistor/Relay. The Blower Motor Relay remains de-energized and current flows through the three resistors and the normally-closed relay contacts to the Blower Motor. The PPL (65) pigtail wire provides operating voltage to the Blower Motor from the Blower Motor Resistor/Relay. The motor's grounding is provides by the BLK (150) pigtail wire back to the resistor/relay. Since the Blower Motor Resistor/Relay is grounded at Ground G103 by the BLK (150) wire, current flow is established and the Blower Motor operates. Voltage drop through the three resistors in the Blower Motor Resistor limits motor operation to its lowest speed.

With the Blower Motor Switch in the Medium 1 position, voltage is applied to the Blower Motor Resistor through the TAN (63) wire. Current must flow through only two resistors to get to the motor. With the increased voltage at the motor, the motor operates at a faster speed.

With the Blower Motor Switch in the Medium 2 position, voltage is applied to the Blower Motor Resistor through the LT BLU (72) wire. Current must flow through only one resistor to get to the motor. With the increased voltage at the motor, the motor operates at a still faster speed.

Automatic reset thermal fuses are provided in the Blower Motor Resistor for each resistor. These thermal fuses will open automatically upon high current flow. Current flow causes heat in the fuse element. When the current flow is high, the heat buildup causes the thermal fuse to open. This stops the current flow. When current flow is stopped. the fuse cools down and resets automatically.

When the Blower Motor Switch is in the HI position, voltage is applied through the ORN (52) wire to the Blower Motor Relay coil. Since the coil is grounded at Ground G103 by the BLK (150) wire, the relay coil energizes. This closes the relay's normally-open contacts and this applies voltage from the HVAC Fuse to the Blower Motor. Because the operating current bypasses the resistors, the Blower Motor operates at its highest speed.