Without Air Conditioning

DESCRIPTION
The base heater system is designed to provide heating, ventilation, windshield defrosting and on some cars, side window defogging. Ram air ventilation is provided on some cars by two outboard vent valves installed in the plenum. These vent valves are controlled by push-pull controls mounted in the instrument panel. When either of these valves are opened, air will enter the passenger compartment from the pressurized plenum and be directed to the floor of the vehicle.

OPERATION
The power-vent, heat, and defrost provisions of the base system are controlled within the heater module. The module itself is composed of two (2) components - a blower air inlet and a heater defroster. The blower air inlet is mounted to the front of the cowl and the heater defroster assembly is mounted to the rear of the cowl. A gasket is used between the two to prevent air, water and noise entrance into the passenger compartment. Air distribution is through a heater outlet, defroster duct, power-vent duct work and outlets.

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:

1. Motor & Fan Assembly (Blower)-Provides and regulates air flow from the air inlet for further processing and/or distribution.

2. Heater Core-Transfers heat from engine coolant to inlet air, heating the inlet air.

3. Temperature Valve-Regulates the amount of air passing through the heater core, controlling the temperature and mix of heated and ambient air.

4. Mode (Defroster) Valve-Regulates the flow and distribution of processed air to the distribution (heater or defroster) ducts.

5. 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 head. 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 head 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 are controllable in all modes (VENT, HEAT, DEFROST) by the switch on the control head.

The power-vent ventilation feature is available in the vent mode. Outside air enters the plenum and is driven by the blower to the temperature valve. In the cold position of the temperature valve, air bypasses the heater core to the vent valve opening and enters the passenger compartment through the vent duct and outlets in the center of the instrument panel. If some heated air is desired, the temperature valve may be opened. This allows mixed (tempered) air to flow out the center vent opening. 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, if so equipped, is provided via ducts in the outboard corners of the instrument panel. Maximum air flow,,from these vents will be in "Heater" mode with reduced air flow in "Defrost" mode.

Varying the mode selector between "Heater" and "Vent" positions 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, depending 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 by the position of the mode valve and control lever. A small amount of air is bled to the side window defogger system.