Manual HVAC

MANUAL SYSTEM
How the Air Delivery (Front) Circuit Works
The heater control panel receives battery voltage at all times through fuse 13. With the ignition switch ON (II), voltage is supplied to the control panel through fuse 3. The control panel is grounded at G401. It controls the blower motor, and supplies a 5 VDC reference voltage to the air mix control motor.

The air mix and front mode control motors each receive inputs from the control panel. The air mix motor regulates the mixture of cold and hot air by varying the position of the heater-evaporator door. The front mode control motor controls the direction and volume of outlet air. The air flow can be directed to the dashboard vents or the corner vents. Both the air mix control motor and front mode control motor are grounded by the control panel.

The recirculation control motor receives battery voltage through fuse 3 when the ignition switch is ON (II). It regulates the position of the fresh/recirc door, and is controlled by two position inputs from the control panel ("Recirc" and "Fresh").

How the Air Delivery (Rear) Circuit Works
Either the rear heater-A/C main switch (front control) or rear heater-A/C passenger control panel (rear control) controls the rear air delivery. With the ignition switch ON (II), voltage is provided to the to the rear mode control motor and the rear mode control motor relay coil through fuse 3.

From the Front (Dashboard Dial)
When you turn the rear heater-A/C main switch counterclockwise (cool mode) from the OFF position, ground is provided through the rear heater-A/C passenger control panel to the BLU/YEL wire of the rear mode control motor. The motor moves the rear mode door so that the air flows from the rear ceiling vents.

When you turn the rear heater-A/C main switch clockwise (hot mode) from the OFF position, ground is provided to the rear mode control motor relay. When the dial is in the middle or high position, ground is provided through the normally closed contacts of the relay to the GRN/RED wire of the rear mode control motor. When the dial is in the low position, ground is also provided to the coil of the relay. Grounding the relay energizes its coil providing ground to the GRN/WHT wire of the motor through the closed contacts of the relay. Regardless of which wire is grounded, the motor moves the rear mode door to a position that directs air flow out the rear floor vents.

From the Rear (Passenger's Control Panel)
When you turn the rear heater-A/C main switch to the rear position (RR), ground is supplied to the rear heater-A/C passenger control panel.

When you turn the air flow control dial (in the rear heater-A/C passenger control panel) to the cool mode, ground is provided to the BLU/YEL wire of the rear mode control motor. The motor moves the rear mode door so that air flows from the rear ceiling vents.

When you turn the air flow control dial (in the rear heater-A/C passenger control panel) to the hot mode, ground is provided to the rear mode control motor relay. When the dial is in the middle or high position, ground is provided through the normally closed contacts of the relay to the GRN/RED wire of the rear mode control motor. When the dial is in the low position, ground is also provided to the coil of the relay. Grounding the relay energizes its coil providing ground to the GRN/WHT wire of the motor through the closed contacts of the relay. Regardless of which wire is grounded, the motor moves the rear mode door to a position that directs air flow out the rear floor vents.