Heater and Air Conditioner

A automatic temperature control (ATC) single zone type heating-air conditioning system is standard equipment on this model. A manually controlled rear air conditioning system is available as a factory installed option.

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

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

Heater Housing:

Vehicles equipped with the factory-installed optional rear air conditioning system use a common roof mounted assembly which includes:
- solenoid valve
- evaporator core
- evaporator temperature sensor
- expansion valve
- blower motor and wheel assembly

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.

Vehicles equipped with the available rear A/C system have an individual temperature control and blower motor speed switches. When the rear A/C system is turned on, a solenoid valve opens the rear refrigerant circuit and activates the blower motor for the rear evaporator. The circulated internal air temperature is measured by a temperature sensor and the temperature value is compared within the rear A/C control module to an adjusted value at the temperature control switch. To prevent icing of the rear evaporator, the temperature switch cuts off the flow of refrigerant through the rear A/C circuit by de-energizing the solenoid valve.

The front and rear A/C systems are designed for the use of non-CFC, R-134a refrigerant only. Both the front and rear systems use an expansion valve to meter refrigerant flow to the evaporator.