Without Air Conditioning

Interior Body Airflow:

Typical Heater System Ductwork:

Floor Heater Ducts:

GENERAL DESCRIPTION
The base heater system is designed to provide heating, ventilation, windshield defrosting and side window defogging. The power-vent, heat, and defrost provisions of the base system are controlled within the heater module. Air distribution is through a heater outlet, defroster duct, and power-vent duct work and outlets.

Six Modes of the Base Heater System
The six modes of the base heater system (off, vent, bi-level, heater, defog and defrost) are controlled by the functional assemblies within the heater module. These assemblies are defined below:

Motor and Fan Assembly (Blower) -Provides and regulates airflow 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.

Vent/Bi-Level Valve -Regulates the distribution of processed air to the vent ducts or heater/defroster valve.

Heater/Defroster Valve -Regulates the flow of processed air into the defroster and/or heater ducts.

Operation
The operation of these assemblies is controlled by the levers and buttons on the control assembly. The temperature lever controls the temerature valve through the potentiometer in the control and an electric motor attached to the heater module. The modes of operation are controlled by push buttons that send an appropriate electrical signal to the four solenoid valves that control the flow of vacuum to the various vacuum valve positioning actuators. Blower speeds (low, medium 1, medium and high) are controlled in all modes (except "off") by two ratchet-type push buttons on the control assembly. The blower is turned off in the "OFF" mode of operation.

Temperature
The temperature of the air entering the vehicle through the heater system may be controlled in all modes of operation from slightly above ambient (full cold position of the temerature lever) to the maximum heat output of the eater system (full hot position of the temperature lever). Side window defogging grilles are in the windshield pillar garnish molding.

Heater Control Assembly:

Modes of Operation
The flow of air from the heater system during the various modes of operation is as follows:

Off -Floor outlet forced air only

Vent -Instrument panel air outlets

B/L -Instrument panel outlets and floor outlets

Heater -Floor outlet and small amount from defroster

Defog -Equal amounts of floor and defrost

Defrost -Defroster outlets