Heater - Without A/C

FRONT BLOWER MOTOR
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 provided 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 Maxi Fuse to the Blower Motor. Because the operating current bypasses the resistors, the Blower Motor operates at its highest speed.

REAR BLOWER MOTOR
The rear Auxiliary Blower Motor controls operate by grounding the Auxiliary Blower Motor Relays through switch contacts. Battery voltage from RR BLOWER Mini Fuse is available at all times to the normally open contacts of each of the three Auxiliary Blower Motor Relays. When one of the relays operates, voltage is applied to the Auxiliary Blower Motor. Since the Auxiliary Blower Motor is grounded at Ground G400 by the BLK (150) wire, the motor operates.

Battery voltage is available from RR HVAC Fuse 12 through the BRN (341) wire to the coils of each of the three Auxiliary Blower Motor Relays. This voltage is available when the Ignition Switch is in the Run position and is used to operate the relays. The Auxiliary Blower Motor Switch grounds the coil of the selected relay through the BLK (150) wire to Ground G400. When the relay coil is grounded through the Auxiliary Blower Motor Switch, current flows through the relay coil. This energizes the relay to close the relay's normally-open contacts. Voltage is supplied to the relay contacts at all times by the RED (1542) wire from the HVAC Maxi Fuse. When the relay contacts close, this voltage is applied to operate the motor.

Placing the Auxiliary Blower Motor Switch in the LOW position grounds the coil of the Auxiliary Blower Motor Low Speed Relay through the DK BLU (1926) / YEL (60) wire. The relay's contacts close and apply operating voltage on the YEL (1176) wire. Current flow is through both the resistors In the Auxiliary Blower Motor Resistor and then through the YEL (1172) wire to the Auxiliary Blower Motor. The voltage drop through the two resistors limits the Auxiliary Blower Motor to its lowest speed.

Placing the Auxiliary Blower Motor Switch in the Medium position grounds the coil of the Auxiliary Blower Motor Medium Speed Relay through the RED (1925) / TAN (63) wire. The relay's contacts close and apply operating voltage on the LT BLU (1072) wire. Current flow is through only one of the resistors in the Auxiliary Blower Motor Resistor and then through the YEL (1172) wire to the Auxiliary Blower Motor. The voltage drop through the single resistor allows the Auxiliary Blower Motor to operate at a higher speed.

Placing the Auxiliary Blower Motor Switch in the HIGH position grounds the coil of the Auxiliary Blower Motor High Speed Relay through the WHT (1924) / ORN (52) wire. The relay's contacts close and apply operating voltage directly on the YEL (1172) wire. Current flow bypasses the resistors in the Auxiliary Blower Motor Resistor. This full battery voltage allows the Auxiliary Blower Motor to operate at its highest speed.