Without Air Conditioning
DESCRIPTION AND OPERATION
Heater Control Functions:
The manual heater and power ventilation control includes a function control lever for Off, Vent, Floor, Mix, and DEFROST that determines the manner in which the system will operate. The system has a temperature control lever for manually setting the desired comfort temperature and a blower switch to control the volume of air movement. Each position of the function control lever and blower switch is detented for positive engagement. The blower switch provides four manually selected blower speeds and may be operated in any position to select the desired amount of air flow.
Temperature Control
Temperature control of the heater and power ventilation system is determined by the position of the temperature control lever (between COOL and WARM) of the control assembly and is accomplished by means of a control cable between the control assembly and the temperature blend door. System air flow is manually controlled by the control assembly. A vacuum selector valve, controlled by the function control lever, distributes vacuum to the various door vacuum motors which in turn direct the air flow through the system.
The system utilizes what is called a "temperature blend" method to provide controlled temperature to the vehicle interior. With this method all outside air flow from the blower passes through the heater case to the plenum assembly. Temperature is then regulated by heating a portion of the outside air and blending it with the remaining cooler outside air to the desired temperature. Temperature blending is varied by the temperature blend door which controls the amount of air that flows through or around the heater core where it is mixed and directed into the distribution plenum. The air is finally directed to the heater ducts, the defroster nozzles, or the instrument panel registers according to the selected function lever position.
System Air Flow
Heater System Air Flow Schematic And Vacuum Control Chart:
Heater System Vacuum Diagram And Selector Test:
Heater System Electrical Wiring Diagram And Continuity Test:
These images contain system vacuum schematics and vacuum motor charts which illustrate vacuum routings and air flow during the various system conditions. Also the system electrical wiring diagram including test information.
OFF
In OFF position the outside air door is in the closed (full vacuum) position. The panel door is in the no vacuum position, and the floor-defrost door is in the floor (full vacuum) position. The blower is off and the temperature blend door maintains a position depending on the temperature control lever position.
VENT
When the function lever is in the VENT position, the outside air door is opened to admit outside air into the system (no vacuum). The panel door is in the PANEL position (vacuum) and the air is distributed out of the instrument panel registers. The floor-defrost door is also applied with full vacuum, directing a small amount of air to the floor area. The outside air can be heated to a higher desired temperature by moving the temperature lever toward WARM.
FLOOR
With the function lever in the FLOOR position, the airflow is directed to the floor outlets with a slight amount directed to the windshield through the defroster outlets.
MIX
With the function lever in the MIX position, the airflow is divided between the defroster outlets and floor ducts. The door positioning is similar to FLOOR except the floor defrost door is in mid-position (partial vacuum) to provide the airflow split.
DEFROST
When the function lever is in the DEFROST position, the panel door and the floor-defrost door are in the full defrost (no vacuum) positions so that all incoming air is directed to the defroster nozzles with a slight bleed to the floor. Maximum heat is obtained by moving the temperature lever to the highest temperature (WARM) position.