Without Air Conditioning
VENTILATION SYSTEMGeneral Motors' cars have a "flow-through" ventilation system. A supply of outside air ("ram" air) flows into the car when it is moving. When the car is not moving, you can get a steady flow of outside air into the car when the heater fan is running.
With the side windows closed, air will flow into the front air inlet grilles, through the car and out the rear air exhaust valves.
Flow-through Ventilation System.:
STANDARD VENTILATION SYSTEM
The standard ventilation system lets you bring outside air into the car in a variety of ways.
To let outside air into the car without heating or cooling it, pull out the two "VENT" knobs under the steering column. The left knob controls air flow through the left air outlet. The right knob controls air flow through the right air outlet. The amount of "ram" air flow will depend on car speed and how far the knobs are pulled out.
For heating or defrosting, close the vents and use the heater control assembly to the right of the steering column. The upper lever selects the air source; the lower lever controls the temperature.
The upper lever has three heater settings:
^ "VENT" - Air will flow through the instrument panel outlets at the speed set by the fan switch. Set the lower (temperature) lever as desired. If heat is added to the incoming air, some air will be diverted to the heater ducts under the instrument panel.
^ "HEATER" - Air flow is through the heater ducts. Set the lower lever for the most comfortable temperature. For the best heat in the rear seat area, move the upper lever to "HEATER," the lower lever to the far right and the fan switch to "HI." Close the windows and "VENT" knobs and be sure the space under the front seat is clear.
^ "DEF" - Most of the air flows through the defroster vents on top of the instrument panel, with some air flow through the heater ducts and side window defroster outlets. For the best defrosting, move the lower lever to the far right and the fan switch to "HI." Refer to the "Operating Tips" for improved heater and efficiency.
To turn the system off, move the upper lever to 'VENT" and the fan switch to "OFF."
OPERATING TIPS
Clear snow and ice from the hood and air inlet in front of the windshield. This helps the heater and defroster work better and reduces the chance of fogging the inside of the windshield.
Run the fan on "HI" for a few moments before driving off. This helps clear the intake ducts of snow and moisture and reduces the chance of fogging the inside of the windows.
Always keep the front inlet grilles clear of obstructions (leaves, ice, snow, etc.).
Always keep the underseat air path clear of objects.
Heat Ventilation System Typical.:
Heater System Air Flow. Typical:
Heater Control-Typical.:
HEATER CONTROL ASSEMBLY
The three modes of the base heater system (Vent, Heat, Defrost) are controlled by the functional assemblies within the heater module. These assemblies are defined below:
^ Motor and Fan Assembly (Blower)-Provides and regulates air flow from the air inlet for further processing and/or distribution.
^ Heater Core-Transfers heat from engine coolant to inlet air, thus heating the inlet air.
^ Temperature Valve-Regulates the amount of air passing through the heater core, thus controlling the temperature and mix of heated and ambient air.
^ Mode (Defroster) Valve-Regulates the flow and distribution of processed air to the distribution (heater or defroster) ducts.
^ Vent Valve-Regulates the flow of non-processed (outside) air into the passenger compartment.
The operation of these assemblies is controlled by the levers and switch on the control assembly. Depending on model application, two (2) or three (3) indexed snap-in cables are attached to the module and control levers.
The temperature cable has the slider type, self-adjust feature. As the temperature lever of the control assembly is cycled through its full range of travel, the cable clip will assume a position assuring that the temperature valve will seat in both extreme positions. The vent and/or defrost cables also have the self-adjusting feature. Blower speeds (OFF - LO - MED - HI) are controllable in all modes (VENT, HEAT, and DEFROST) by the switch on the control assembly.
Blending air between modes can be done by varying the mode selector. Varying the selector between "Heat" and "Defrost" will allow more air or less air to be directed out either the defroster outlet or the heater outlet. The closer the mode selector is positioned to the "Heater" position, the larger the amount of air coming out the heater outlet. The closer the mode selector is positioned to "Defrost," the larger the amount of air going to the windshield. The temperature of this air is governed by the temperature lever position. Side window defogging is provided via ducts in the outboard corners of the instrument panel. Maximum air flow from these vents will be in the "Heater" mode with reduced air flow in the "Defrost" mode.
Varying the mode selector between "Heater" and "Vent" positions likewise varies the proportion of air coming out the heater outlet and the center vent outlets. With the selector in some midway position, air coming out the center vent outlets will be ambient temperature, while air out the heater outlet will be mixed warm air, its temperature depending on temperature lever position.
In the Heat and Defrost mode, outside air is driven by the blower to the temperature valve which, dependent upon its position as controlled by the operator, distributes all or some portion of the inlet air through the heater core. The vent valve will prevent air entry into the vent duct and direct this ambient air to the mix portion of the heater module. The air is thus heated, mixed and then directed into either the defroster duct or the heater outlet depending on the position of the mode valve and control lever. A small amount of air is bled to the side window defogger system.