Description and Operation

The heater system uses a single heater case assembly located under the instrument panel (04320) . This heater case contains:

• The heater core (18476) .
• A/C Air Temperature Control Door.
• Windshield Defroster Door.

all located downstream from the A/C blower motor assembly. The A/C Air Temperature Control door is operated by a new pull-pull cable. The windshield defroster door is vacuum-actuated. The A/C blower motor can be replaced without removing the heater case from the vehicle.

Outside air enters the heater case assembly through the cowl opening and is forced by the A/C blower motor assembly through the heater case assembly.

• The air passes around and/or through the heater core , is blended (if passed through the heater core ), then directed, depending upon the position of the air discharge door assembly, to the panel by way of the heater air plenum chamber (18471) .
• From there, the airflow is directed to the floor or to the defroster outlets.

The heater air plenum chamber :

• Is positioned at the heater case.
• Contains a polyurethane foam gasket to form a seal between the heater air plenum chamber and the heater case opening.
• Is held in place by a retaining screw located at each side. Each A/C evaporator register duct (19B680) is installed with two screws. The LH A/C evaporator register duct is secured to the cross car beam. The RH A/C evaporator register duct is secured to the instrument panel adjacent to the RH register. The heater air plenum chamber contains two center A/C register duct openings as an integral part of the assembly. The instrument panel must be removed for access to the heater air plenum chamber .

The RH and LH A/C evaporator register ducts provide a path for air, forced from the heater air plenum chamber by the A/C blower motor, to flow to the outboard instrument panel A/C registers (19893) .

• Each A/C evaporator register duct connects to the instrument panel with one screw and at the inboard end of the A/C evaporator register duct to the heater air plenum chamber at the overlap.
• The instrument panel must be removed for access to the retaining screws.

The side A/C side window demister and hoses (19E630) :

• Provide air to the side glass when operating in the defrost and floor functions.
• Are attached to the instrument panel with two screws each.