A manual temperature control (MTC) single zone type heating-A/C system, MTC front and rear heating-A/C system
or a fully adjustable automatic temperature control (ATC) front and rear heating-A/C system is available on this
vehicle.

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
7 - Cooling for more information before opening or attempting any service to the engine cooling system.

FRONT HEATING AND A/C SYSTEM

All vehicles are equipped with a common front heater,
ventilation and air conditioning (HVAC) housing (1).
The front heating-A/C system combines A/C, heating,
and ventilating capabilities in a single HVAC housing
mounted within the passenger compartment under the
instrument panel. The front HVAC housing includes:

•

Recirculation-air door and actuator (2)

•

Blower motor (3)

•

Blower motor resistor (MTC) or blower motor
power module (ATC) (4)

•

Evaporator temperature sensor (5)

•

Blend-air door and actuator (6)

•

Mode-air doors and actuators (7)

•

Heater core (8)

•

A/C evaporator (9)

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HVAC - SERVICE INFORMATION

Based upon the mode selected, conditioned air can exit the front HVAC housing through one or a combination of
the three main housing outlets: defrost, panel or floor. The defrost outlet is located on the top of the HVAC housing,
the panel outlet is located on the top of the HVAC housing and the floor outlet is located on the bottom of the HVAC
housing. Once the conditioned air exits the HVAC housing, it is further directed through molded plastic ducts to the
outlets within the vehicle interior. These outlets and their locations are as follows:

•

Defroster Outlet - A single large defroster outlet is located in the center of the instrument panel top cover,
near the base of the windshield.

•

Side Window Demister Outlets - There are two side window demister outlets, one is located at each out-
board end of the instrument panel top cover, near the belt line at the A-pillars.

•

Panel Outlets - There are six panel outlets in the instrument panel, one located near each outboard end of the
instrument panel facing the rear of the vehicle and two located at each side of the instrument panel center
bezel.

•

Floor Outlets - There are four floor outlets, one located above each side of the floor panel center tunnel near
the dash panel and one behind each front seat.

REAR HEATING AND A/C SYSTEM

The manual temperature control (MTC) front and rear
heating-A/C system, and the automatic temperature
control (ATC) front and rear heating-A/C system are
equipped with a common rear heater and A/C housing
(1) that combines A/C and heating capabilities into a
single unit mounted within the passenger compartment
behind the right quarter interior trim panel. The rear
HVAC housing includes:

•

Blower motor (2)

•

Blower motor resistor (3)

•

A/C evaporator (4)

•

A/C expansion valve (5)

•

Heater core (6)

•

Blend door and actuator (7)

•

Mode door and actuator (8)

Based upon the rear temperature selected, conditioned air can exit the rear HVAC housing through one or a com-
bination of the two rear HVAC housing outlets: ceiling or floor. The ceiling outlet is located at the top-front of the
HVAC housing and the floor outlet is located at the front of the HVAC housing. Once the conditioned air exits the
rear HVAC housing, it is further directed through molded plastic ducts to the outlets at the rear of the passenger
compartment. These outlets and their locations are as follows:

•

Ceiling Outlets - There are four ceiling outlets in the headliner. One located at each outboard side of the
intermediate seat position and one located in front of each rear seat postion.

•

Floor Outlet - There is one floor outlet in the right quarter interior trim panel located behind the right rear door
area.

OPERATION

The standard front and the optional rear heating-A/C systems used in this vehicle are blend-air type systems. In a
blend-air heating-A/C system, a blend-air door controls the amount of conditioned air that is allowed to flow through,
or around, the heater core. A temperature control determines the discharge air temperature by operating an electric
actuator, which operates the blend-air door. This allows an almost immediate control of the output air temperature of
the systems. Both the front and rear A/C systems are designed for the use of non-CFC, R-134a refrigerant and use
an A/C evaporator to cool and dehumidify the incoming air prior to blending it with the heated air.

HVAC - SERVICE INFORMATION

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FRONT SYSTEM

The standard front heating-A/C system pulls outside
(ambient) air through the cowl opening at the base of
the windshield, then into the air inlet housing and
through the A/C evaporator (3). Air flow can be
directed either through or around the heater core (1).
This is done by adjusting the blend-air doors (2) with
the temperature controls located on the A/C-heater
control in the instrument panel. The air flow can then
be directed from the panel, floor and defrost outlets in
various combinations using the mode control located
on the A/C-heater control. Air flow velocity can be
adjusted with the blower speed control located on the
A/C-heater control.

The outside (fresh) air intake can be shut off by selecting the Recirculation Mode with the mode control. This will
operate an electrically actuated recirculation-air door (4) that closes off the fresh air intake and recirculates the air
that is already inside the vehicle.

The A/C compressor can be engaged in any mode by pressing the snowflake, A/C on/off button. It can also be
engaged by placing the mode control in the mix to defrost positions. This will remove heat and humidity from the air
before it is directed through or around the heater core. The mode control on the A/C-heater control is used to also
direct the conditioned air to the selected system outlets. The mode control uses two electric actuators to control the
mode-air doors (5 and 6).

The defroster outlet receives airflow from the HVAC housing through the molded plastic defroster duct, which con-
nects to the HVAC housing defroster outlet. The airflow from the defroster outlet is directed by fixed vanes in the
defroster outlet grille and cannot be adjusted. The defroster outlet grille is integral to the instrument panel top cover.

The side window demister outlets receive airflow from the HVAC housing through the molded plastic demister ducts.
The demisters direct air from the HVAC housing through the outlets located on the top corners of the instrument
panel. The airflow from the side window demister outlets is directed by fixed vanes in the demister outlet grilles and
cannot be adjusted. The side window demister outlet grilles are serviceable from the instrument panel. The demis-
ters operate when the mode control is positioned in the bi-level, floor, floor-defrost and defrost settings.

The instrument panel outlets receive airflow from the HVAC housing through a molded plastic main panel duct,
center panel duct and two end panel ducts. The two end panel ducts direct airflow to the left and right instrument
panel outlets, while the center panel duct directs airflow to the four center panel outlets. Each of these outlets can
be individually adjusted to direct the flow of air.

The floor outlets receive airflow from the HVAC housing through the floor distribution ducts. The front floor outlets
are integral to the molded plastic floor distribution duct, which is secured to the bottom of the HVAC housing. Two
plastic rear floor distribution ducts attach to the floor distribution duct and provide conditioned air to the intermediate
seating positions. The floor outlets cannot be adjusted.

NOTE: It is important to keep the air intake opening clear of debris. Leaf particles and other debris that is
small enough to pass through the cowl opening screen can accumulate within the HVAC housing. The
closed, warm, damp and dark environment created within the housing is ideal for the growth of certain
molds, mildews and other fungi. Any accumulation of decaying plant matter provides an additional food
source for fungal spores, which enter the housing with the fresh intake-air. Excess debris, as well as objec-
tionable odors created by decaying plant matter and growing fungi can be discharged into the passenger
compartment during heater-A/C operation if the air intake opening is not kept clear of debris.

This A/C system uses an A/C expansion valve (TXV) to meter the flow of refrigerant to the A/C evaporator. To
maintain minimum evaporator temperature and prevent evaporator freezing, an evaporator temperature sensor input
is supplied to the A/C-heater control. In turn, the powertrain control module (PCM) cycles the A/C compressor clutch
off and on as necessary to optimize A/C system performance and to protect the A/C system from evaporator freez-
ing.

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