System Description

HEATING & AIR CONDITIONING

Fig. 1 HVAC Housing - Dual Zone Shown (Typical - Single Zone):

Heater And Air Conditioner
All vehicles are equipped with a common HVAC housing assembly. The system combines air conditioning, heating, and ventilating capabilities in a single unit housing mounted under the instrument panel.

The heater air conditioner are blend-air type systems. In a blend-air system, a blend door controls the amount of unconditioned air (or cooled air from the evaporator on models with air conditioning) that is allowed to flow through, or around, the heater core. A temperature control knob on the A/C Heater control panel determines the discharge air temperature by controlling an electric actuator, which moves the blend door. This allows an almost immediate control of the output air temperature of the system.

The mode control knob on the A/C Heater control panel is used to direct the conditioned air to the selected system outlets. Both mode control switches use electric actuators to control the mode doors.

On all vehicles, the outside air intake can be shut off by selecting the Recirculation Mode with the mode control knob. This will operate a electric actuated recirculation door that closes off the outside fresh air intake and recirculates the air that is already inside the vehicle.

The air conditioner for all models is designed for the use of non-CFC, R-134a refrigerant. The air conditioning system has an evaporator to cool and dehumidify the incoming air prior to blending it with the heated air. This air conditioning system uses a fixed orifice tube in the liquid line near the condenser outlet tube to meter refrigerant flow to the evaporator coil. To maintain minimum evaporator temperature and prevent evaporator freezing, the A/C Fin Probe which is located in the evaporator cycles the compressor clutch by sending an A/C request to the JTEC which in turn processes this piece of information and if all conditions are met cycles the compressor clutch.