2002 GMC YUKON air conditioning

2-91 Low Coolant
This message is displayed
when the cooling system is
low on coolant.
The engine may overheat. See ªEngine Coolantº in the
Index and have your vehicle serviced as soon as you can.
Check Coolant Temp
This message is displayed
when the cooling system
temperature gets hot.
Check the coolant temperature gage and the coolant
level. See ªEngine Coolantº and ªEngine Coolant
Temperature Gageº in the Index. See ªEngine
Overheatingº in the Index for further information.
Engine Overheated
This message is displayed
when the cooling system
temperature gets too hot.
This message will be displayed after the air conditioning
system has automatically turned off for the engine
coolant protection mode. See ªEngine Overheatingº
in the Index for further information.
Reduced Engine Power
This message is displayed
when the cooling system
temperature gets too hot
and the engine further
enters the engine coolant
protection mode.
If your vehicle is equipped with the 8.1L engine, this
light may come on because of an electronic throttle
control system fault. See ªEngine Overheatingº in the
Index for further information.

3-3 Heater and Air Conditioning Comfort
Controls (If Equipped)
Fan Knob
The knob on the left side of the control panel adjusts the
fan speed. To increase airflow, turn the knob clockwise.
To decrease airflow, turn it counterclockwise. To turn
the fan off, turn the knob to OFF.
Temperature Knob
The middle knob on the control panel lets you select the
temperature of the air flowing into the passenger area.
Turn the knob clockwise toward the red area for warmer
air. Turn the knob counterclockwise toward the blue area
for cooler air.Mode Knob
The right knob on the control panel allows you to
choose the direction of air delivery.
(Vent): This setting directs the air through the
instrument panel outlets and the center floor console
(if equipped).
(Bi-Level): Air is delivered through the
instrument panel outlets and center floor console outlets
(if equipped) as well as the floor outlets. The air flow
can be divided between instrument panel and floor
depending upon where the knob is placed between the
settings. Pressing the A/C button while in this mode
causes cooler air to come out of the instrument panel
outlets and center floor console outlets (if equipped) and
warmer air to come out of the floor outlets.
(Floor): This setting directs most of the air
through the floor outlets and center floor console outlets
(if equipped), as well as some air through the windshield
defroster outlets and side window defroster outlets. If air
from the center floor console outlets is not desired, turn
the vents off at the console.

3-4
(Blend): Airflow is delivered through the floor
outlets, center floor console outlets (if equipped), the
windshield defroster outlets and the side window
defroster outlets. The air conditioning compressor may
run to dehumidify the air to prevent window fogging.
(Defrost):This setting directs most of the
air through the windshield defroster outlets, side
window defroster outlets and some air through the
floor and center floor console outlets (if equipped).
If air from the center floor console is not desired, or
more defroster performance is desired, turn the vents
off at the console. When in defrost mode, the air
conditioning compressor may run to dehumidify
the air and limit window fogging.
Mode Buttons
(Outside Air): Press this button to direct the
system to use outside air.
Pressing the outside air button will cancel the
recirculation button.
(Recirculation): Press this button to limit the
amount of outside air entering the vehicle. This is
helpful when you are trying to limit odors entering the
vehicle or attempting to quickly cool down the interior.
Pressing recirculation will recirculate air continuously.
Recirculation is used when the fan is OFF to limit odors,
outside air and dust from entering your vehicle. All
button lights will go off. The last setting selected will
activate when the blower is turned back on.
Pressing the recirculation button will cancel the outside
air button. To return to normal operation and to prevent
stale air, be sure to return to outside air.
Between floor and blend mode, outside air is forced to
reduce window fogging. If the recirculation button is
pressed, the LED indicator will flash three times
indicating that forced outside air is activated and
recirculation is not available.

3-5
A/C (Air Conditioning):Press this button to turn
Fan Cont rol

3-6
When both the fan control and mode knobs are in the
AUTO position, the system will then automatically
maintain the desired cabin temperature as selected.
Manual control of functions is also available.
Temperature Knob
The middle knob on the control panel lets you select the
desired air temperature in your vehicle. This knob will
allow you to adjust the interior air temperature
independent of the function knob setting. Move the knob
clockwise toward 82
F (28
C) for warmer air. Move the
knob counterclockwise toward 66
F (19
C) for cooler
air. When the system is set for automatic operation,
sensors will control the fan speed.
Full Hot: If you turn the temperature knob past 82
F
(28
C), the system will go into the ªfull hotº mode. The
system will remain at that maximum heating setting and
the fan will blow at the speed the fan knob is set to. If
the fan is in AUTO, it will run at full speed.
Full Cold: If you turn the temperature knob past 66
F
(19
C), the system will go into the ªfull coldº mode.
The system will remain at that maximum cooling setting
and the fan will blow at the speed the fan knob is set to.
If the fan is in AUTO, it will run at full speed.Mode Knob -- Manual Operation
The right knob on the control panel allows you to
choose the direction of air delivery.
You can choose to set the climate control system
yourself, or let the system work for you by placing the
system in AUTO mode. See ªMode Knob
-- Automatic
Operationº later in this section.
(Vent): This setting directs most of the air through
the instrument panel outlets and a small amount through
the floor outlets.
(Bi-Level): Air is delivered through the floor
outlets as well as the instrument panel outlets.
(Floor): This setting directs most of the warmed
air through the floor outlets and some air through the
windshield defroster outlets.
(Blend): Airflow is divided equally between the
floor outlet and the windshield defroster outlets. The air
conditioning compressor may run to dehumidify the air
to prevent window fogging.

3-7
(Defrost): This setting directs most of the air
through the windshield defroster outlets with air flow
also delivered from the side window and floor outlets.
When in defrost mode, the air conditioning compressor
may run to assist in dehumidifying the air and limit
window fogging.
Mode Buttons
(Outside Air): Press this button to force the
system to use outside air. Press is again to close off the
outside air.
Pressing the outside air button will cancel the
recirculation button.
(Recirculation): Press this button to limit the
amount of outside air entering your vehicle. This is
helpful when you are trying to limit odors entering your
vehicle or attempting to quickly cool down the interior.
Recirculation may be selected with the fan control in
OFF to limit odors, outside air and dust from entering
your vehicle.
Pressing the recirculation button will cancel the outside
air button.
A/C (Air Conditioning):Press this button to turn
the air conditioning on and off. The system will cool and
dehumidify the air inside the vehicle when the A/C light
is on. When in AUTO, the A/C is automatically engaged
when necessary.
Air conditioning will be automatically disabled when
the outside air temperature drops below a level at which
air conditioning is ineffective.
Mode Knob
-- Automatic Operation
When the system is set for automatic operation,
sensors will control the air delivery mode. Air will
come primarily from the floor or instrument panel
outlets, with some air directed to the windshield to
prevent fogging.
When the system is in AUTO mode, the air conditioning
light will turn on, and the recirculation and outside air
lights turn off. With the system in full auto control
(both the fan and mode knobs in AUTO), you still have
the ability to override any function. However, continually
overriding the outside air or the A/C compressor will limit
the ability of the system to cool the vehicle quickly.

3-8
If you push a button for a function which is not
available, the light next to that button will flash three
times to alert you that it's not available.
To find your comfort zone, start with the 74
F (23
C)
setting and allow about 20 minutes for the system to
adjust the temperature if necessary.
With the automatic setting, the air conditioning
compressor automatically cycles when needed to cool
the air. In cold weather, when the system senses the need
for heat, the airflow will be directed out of the floor
outlets. As the interior temperature approaches a desired
setting, the fan speed will decrease. To maintain interior
comfort, the airflow will adjust between the instrument
panel air outlets and floor outlets. On bright sunny days
in cool weather, the airflow may come out of the air
conditioning and floor outlets (bi
-level mode) to
maintain comfort and prevent stuffiness.To avoid blowing cold air in cold weather, the system will
delay turning on the fan until warm air is available. The
length of delay depends on the outside air temperature,
engine coolant temperature or the time since the engine
was last started. As the coolant warms up, the fan speed
will gradually increase and air will flow from the floor
outlets, with some airflow to the windshield to prevent
fogging under most normal conditions.
Be careful not to put anything over the solar sensor
located around the center of the instrument panel.
This sensor is used by the automatic system to
regulate temperature.

3-9 Rear Air Conditioning and Heating Systems
(If Equipped)
If your vehicle has one of these systems, you can
increase and decrease the airflow at the rear vents.
Depending on the system you have and the setting
selected, you can send cooled or heated air to the rear
of the vehicle.
Rear Air Conditioning and Rear Heater
(With Sunroof)
Your vehicle has the rear air conditioning and rear heater
system combination. Controls are provided to regulate
temperature, air delivery location and fan speed.
Front ControlTo adjust the airflow speed, turn the fan control knob
located on the left side to the desired setting.
To regulate the airflow location, adjust the right knob on
the control. Turn the knob clockwise for floor vent
airflow or counterclockwise for headliner vent airflow.
Generally, the instrument panel outlets are used for air
conditioning and the floor vents for heating. The control
knob can be set to any blend setting.
To adjust the air temperature, turn the temperature knob
on the center of the control panel.
For warmer air, turn the knob clockwise toward red. For
cooler air, turn the knob counterclockwise toward blue.