Heating Systems and Control Doors

The flow of outside air into the heating system begins at the upper cowl. From there, the air proceeds through the inlet duct of the heater assembly and into the case, where it is distributed into the vehicle according to the settings of the function, temperature and blower speed selector knobs.

Incoming air may flow through the system at a "ram air" rate, which is based on the rate at which the vehicle is moving in a forward direction. On the other hand, the rate of the incoming ram air may be accelerated by the blower motor, depending on the blower speed selected: LOW, MEDIUM LOW, MEDIUM HIGH or HIGH.

The heating system includes a heater core, which receives heat from the hot coolant directed through it by the engine cooling system. The amount of heat available to the passenger compartment is dependent upon the position of a cable-operated temperature blend door. When the temperature door is fully opened (full HOT position), all of the incoming air circulates through the core. Conversely, when the temperature door is fully closed (full COLD position), all of the incoming air bypasses the heater core and there is no heating effect.

There are three additional damper-type doors in the heating system: a FLOOR/DEFROST door, a PANEL/DEFROST door and an OUTSIDE/RECIRC door. Each of these doors is vacuum-controlled.

The FLOOR/DEFROST and PANEL/DEFROST doors direct air into the passenger compartment through the applicable ducts and registers. The OUTSIDE/RECIRC door shuts off the input of outside air when the function selector is in the OFF position, and allows the input of outside air when any position except OFF is selected.