Description

An automatic temperature control (ATC) single zone type heating-A/C system is standard equipment on this model.

To maintain the performance level of the heating, ventilation and air conditioning (HVAC) system, the engine cooling system must be properly maintained. The use of a bug screen is not recommended. Any obstructions in front of the radiator or A/C condenser will reduce the performance of the A/C and engine cooling systems.

The engine cooling system includes the radiator, thermostat, radiator hoses and the engine coolant pump. Refer to Cooling for more information before opening or attempting any service to the engine cooling system.

Ventilation Housing:

All vehicles are equipped with a common ventilation housing located in the engine compartment which includes:
- Blower motor
- Blower motor resistor block
- Recirculation door and actuator

Heater Housing:

All vehicles are also equipped with a common heater housing mounted under the instrument panel which includes:
- Heater core
- Evaporator core
- Evaporator temperature sensor
- Expansion valve
- Air outlet temperature sensor
- Mode doors

Denso 10S17 A/C Compressor:

Some vehicles are equipped with an additional Denso 10S17 A/C compressor mounted to the engine which is used for the optional rear A/C system and various add-on A/C systems.

Heater Booster:

A heater booster is used to aid in warming the engine coolant. The heater booster system can be switched on while the vehicle is being driven to help the engine reach its normal operating temperature quickly and will help aid in heating up the air within the passenger compartment quickly when requested by the operator.

Outside air enters the vehicle through the hood opening at the base of the windshield, and passes through the ventilation housing located in the engine compartment into the heater housing located behind the instrument panel. Air flow velocity is adjusted with the blower motor speed selector thumbwheel on the A/C-heater control. The air intake openings must be kept free of snow, ice, leaves, and other obstructions for the HVAC system to receive a sufficient volume of outside air.

The automatic temperature control (ATC) system controls interior temperature by taking actual values from the temperature sensors and the CAN bus and comparing them to the nominal value of the temperature control switch. The electric pulsed heater valve is then energized depending on the requested quantity of heat and an electrically-operated water pump gives a nearly constant water flow for exact temperature regulation. If the solenoid is not energized, the coolant circuit to the heat exchanger is fully open. To control the temperature the solenoid valve is pulsed by the ATC in periods of four seconds.

The mode control knob on the A/C-heater control is used to direct the conditioned air flow to the selected air outlets. The mode control knob operates the mode doors by cables connected to the mode doors.

When the outside air contains smoke, odors, high humidity, or if rapid cooling is desired, interior air can by recirculated by selecting the Recirculation Mode with the mode control knob. The mode control knob operates the recirculation door through use of a vacuum actuator. When the Recirculation Mode is selected, the recirculation door is closed to prevent outside air from entering the passenger compartment.

To maintain minimum evaporator temperature and prevent evaporator freezing, an evaporator temperature sensor is used.

The A/C system is designed for the use of non-CFC, R-134a refrigerant only and uses an expansion valve to meter refrigerant flow to the evaporator.

PLUMBING
The refrigerant lines and hoses are used to carry the refrigerant between the various air conditioning system components. A barrier hose design with a nylon tube, which is sandwiched between rubber layers, is used for the R-134a air conditioning system on this vehicle. This nylon tube helps to further contain the R-134a refrigerant, which has a smaller molecular structure than R-12 refrigerant. The ends of the refrigerant hoses are made from lightweight aluminum or steel, and commonly use braze-less fittings.

Any kinks or sharp bends in the refrigerant plumbing will reduce the capacity of the entire air conditioning system. Kinks and sharp bends reduce the flow of refrigerant in the system. A good rule for the flexible hose refrigerant lines is to keep the radius of all bends at least ten times the diameter of the hose. In addition, the flexible hose refrigerant lines should be routed so they are at least 80 millimeters (3 inches) from the exhaust manifold.

High pressures are produced in the refrigerant system when the air conditioning compressor is operating. Extreme care must be exercised to make sure that each of the refrigerant system connections is pressure-tight and leak free. It is a good practice to inspect all flexible hose refrigerant lines at least once a year to make sure they are in good condition and properly routed.

The refrigerant lines and hoses cannot be repaired and, if faulty or damaged, they must be replaced.