For 1990-2009 cars

### Heater, Ventilation and Air Conditioning System Operation

The A/C system provides the following features:

• | Cooled or dehumidified air for the comfort of the occupants

• | Power ventilation

• | Windshield defrosting

• | Side window defrosting

During most operating conditions, outside air enters the vehicle in the following manners:

• | The blower motor pulls in outside air through the heater and air conditioning modules.

• | The forward movement of the vehicle forces in outside air.

Air is pushed by the blower motor, along the following path:

1. Through the evaporator core
2. Through the heater core
3. Into the passenger compartment

If the ambient temperature is above 7°C (45°F), the refrigeration system will chill the evaporator to almost freezing. This action permits the operation of the following components:

• | The air conditioner

• | The defroster

As the air passes through the evaporator, the air temperature drops. Air moisture condenses on the evaporator core fins. A gravity feed through a drain hole removes the moisture from the vehicle. This action dehumidifies the air.

From the evaporator, some or all of the air may pass through the heater core. If the system is in the heating mode, the engine coolant warms the air. Any of the air which is not to be heated will mix with the heated air before entering the passenger compartment.

If the user selects the maximum air conditioning mode, most of the air that enters the blower motor is from the passenger compartment (recirculated). The air from the passenger compartment is usually cooler than the outside air. The other modes use outside air.

### Side Window Defogging

Air is supplied to the side window defogger outlets in all modes except the following modes:

• | OFF

• | UPPER

The side window defogger outlets are located at both ends of the instrument panel.

### Auxiliary Heater (C36)

An auxiliary heating option is available for vehicles sold in Canada. The auxiliary heating option includes a separate blower module which houses the following components:

• | A heater core

• | A blower motor

This auxiliary heating option is standard equipment on all Canadian vehicles that are equipped with third-row seating. The auxiliary heater provides an increased level of comfort for passengers in the rear of the vehicle. Major components of the auxiliary heating system include:

• | Additional underhood heater hoses/pipes

• | Auxiliary heater water shutoff valve

• | Front-to-rear heater hoses/pipes

• | Rear fan-master control

• | Rear fan-temperature control

• | Heater A/C module which consists of the following components:

- | The blower motor

- | The blower motor resistor

- | The rear temperature valve electric actuator

- | The heater inlet hoses

- | The heater outlet hoses

- | A heater core

### Rear Air Conditioning (C34)

#### Refrigerant System -- With Rear A/C

(1) | Compressor
(2) | Front Condenser
(3) | Rear Liquid Line
(4) | Front Evaporator
(5) | Accumulator
(6) | Rear Vapor Line
(7) | Thermal Expansion Valve
(8) | Rear Evaporator
(9) | Expansion Tube (Orifice)
(10) | Front Liquid Line
(11) | Pressure Relief Valve

A rear air conditioning option (C34) is available. This option provides an increased level of comfort for passengers in the rear of the vehicle. The rear air conditioning system includes the following major components:

• | Additional underhood heater hoses/pipes

• | Front-to-rear heater hoses/pipes

• | Additional underhood refrigerant hoses/pipes

• | Rear fan-master control

• | Rear fan-temperature control

• | A heater A/C module which consists of the following components:

- | The blower motor

- | The blower motor resistor

- | The rear inlet hoses

- | The rear outlet hoses

- | The refrigerant hoses (evaporator core inlet and outlet)

- | The evaporator core

- | A thermal expansion valve

The rear heater A/C module is an independent heating and air conditioning system. The rear heater A/C module is located behind the left quarter trim panel. Coolant flow is routed through the additional heater hoses/pipes as follows:

1. From the engine compartment
2. Under the vehicle
3. To the rear heater A/C module
4. To the rear heater core

The front air conditioning system directly supplies refrigerant flow to the rear evaporator. The front air conditioning system has extended hoses and pipes which are routed as follows:

• | From the engine compartment

• | Under the vehicle

• | To the heater A/C module

### VDOT A/C System

The Variable Displacement Orifice Tube (VDOT) refrigeration system has a V5 compressor. The V5 compressor used on the 3400 engine can match the automotive air conditioning demand under any conditions without cycling.

The basic compressor mechanism is a variable angle wobble-plate with five axially oriented cylinders.

A bellows actuated control valve determines the compressor displacement. This control valve is located in the rear head of the compressor, and senses the suction pressure of the compressor.

The crankcase suction pressure differential controls the following:

• | The wobble-plate angle

• | The compressor displacement

The following actions occur when the A/C capacity demand is high:

• | The suction pressure is above the control point.

• | The valve maintains a bleed from the crankcase to suction.

• | No crankcase-suction pressure differential exists.

• | The compressor has maximum displacement.

The following actions occur when the A/C capacity demand is lower and the suction pressure reaches the control point:

• | The valve bleeds discharge gas into the crankcase.

• | The valve closes off a passage from the crankcase to the suction plenum.

A force balance on the five pistons controls the angle of the wobble plate. A slight increase of the crankcase-suction pressure differential changes the total force on the pistons. This change affects the movement around the wobble-plate pivot pin and reduces the angle of the wobble plate.

The compressor has a unique lubrication system. The crankcase-suction bleed is routed through the rotating wobble-plate. This routing permits lubrication of the wobble-plate bearing. The rotation acts as an oil separator. Some of the oil is removed from the crankcase-suction bleed and rerouted to the crankcase. The rerouted oil can lubricate the compressor mechanism.

The compressor is cut off when the following conditions exist:

• | Wide-open throttle

• | Low idle speed

• | Low air temperature

• | High power steering loads

For A/C Electrical System diagnosis, refer to HVAC Compressor Controls in Electrical Diagnosis.

The refrigerant in the system flows from the high pressure side to the low pressure side of the expansion (orifice) tube when the following conditions exist:

• | The engine is turned off.

• | The A/C system is operating.

The refrigerant continues to flow until the pressure is equalized. This action may cause a faint sound of liquid flowing (hissing) for 30 to 60 seconds. The sound is a normal condition.

### Heater A/C Controls

The knobs and buttons on the control head control the operation of the A/C system. The compressor clutch and blower are connected electrically to the control head by a wiring harness. Air flow is provided at one of 5 available blower speeds. Cooled and dehumidified air is available in all modes. A/C compressor operation is forced in the following modes:

• | Defog mode

• | Defrost mode

A/C compressor operation is available in the remaining modes by pushing the A/C button-to-light indicator. Low ambient temperatures will not permit the operation of the A/C compressor.

The temperature knob controls the temperature valve through a potentiometer in the control. Vacuum actuators control the modes of operation. The vacuum actuators control the flow of vacuum on the various vacuum valve positioning actuators. The knob on the left controls the blower motor speed. Turning the knob to the right increases the motor speed. The blower is turned off in the OFF position.

Temperature valve position is independent of mode selection.