Without Air Conditioning

Typical Heater System Duct Work:

Main Air Distribution Duct:

Rear Compartment Air Outlet Ducts:

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

Modes Of The Base Heater System
The six modes of the base heater system (OFF, VENT, BI-LEV, HEAT, BLEND, and DEFROST) are controlled by the functional assemblies within the heater module. These assemblies are defined below:

1. Motor and 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, thus heating the inlet air.
3. Temperature Valve - Regulates the amount of air passing through the heater core, thus controlling the temperature and mix of heated and ambient air.
4. Mode Valves - Regulates the distribution of processed air to the vent ducts' heater, and defroster valves.

The operation of these assemblies is controlled by the lever and buttons on the control head.

Heater Control Assembly:

CONTROLS
The temperature lever controls the temperature valve through the potentiometer in the control assembly and electric motor attached to the heater module. The modes of operation are controlled by pushbuttons that send an appropriate electrical signal to the five 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 pushbuttons on the control head. The lower is turned off in the "OFF" mode of operation.

Temperature Range
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 temperature lever) to the maximum heat output of the heater system (full hot position of the temperature lever). Side window defogging grilles are in the windshield side upper garnish molding.

Interior Body Air Flow And Exit - Typical Sedan:

AIR DISTRIBUTION SYSTEM
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 Bi-LEV - instrument panel outlets and floor outlets.
HEAT - Floor outlet and small amount from defroster and side window defogger.
BLEND - Equal amounts of floor and defrost and small amount from side window defogger.
DEFROST - Defroster outlets and small amounts from heater and side window defogger.