
A. Fan Control
B. Temperature Control
C. Air Delivery Mode
ControlD. Rear Window
Defogger
On hot days, open the windows to let hot inside air
escape; then close them. This helps to reduce the time
it takes for the vehicle to cool down. It also helps the
system to operate more efficiently.
Air Delivery Mode Control:Turn clockwise or
counterclockwise to change the direction of the airflow
inside the vehicle.
Select from the following modes:
<(Maximum Air Conditioning):For maximum
cooling. The system goes into recirculation mode and
helps to maximize the air conditioner’s performance and
the vehicle’s fuel economy. This setting also cools the air
the fastest.
Y(Air Conditioning):For normal cooling on hot days.
Outside air is cooled and directed to the instrument
panel vents.
)(Bi-Level Air Conditioning):Air is divided between
the floor and instrument panel vents. The air conditioning
compressor cycles continuously in this setting as long as
the outside temperature is warm enough to activate the
compressor.
H(Vent):Air is directed to the instrument panel vents.
6(Floor):Air is directed to the floor vents. Use this
mode to send air to the rear of the vehicle. Keep the area
under the front seats free of objects that could obstruct
airflow to the rear of the vehicle.
-(Defog):This mode clears the windows of fog or
moisture. Outside air is directed to the floor and
defroster outlets. Adjust the temperature knob for
warmer or cooler air. The air conditioning compressor
may operate in this setting to dehumidify the air.
0(Defrost):This mode removes fog or frost from the
windshield more quickly. Air is directed to the
windshield, with some going to the floor outlets and
front side windows. The air conditioning compressor may
operate in this setting to dehumidify the air.
The temperature knob should be in the red area and the
fan control toward high. Do not drive the vehicle until all
the windows are clear. Vehicles With Air Conditioning
3-21

Rear Window Defogger
For vehicles with a rear window defogger, a warming
grid is used to remove fog or frost from the rear window.
The rear window defogger only works when the
ignition is in ON/RUN.
<(Rear):Press to turn the rear window defogger on
or off. An indicator light comes on to show that the
rear window defogger is on. Be sure to clear as much
snow from the rear window as possible.
The rear window defogger turns off several minutes
after the button is pressed. The defogger can also be
turned off by turning off the engine.
Notice:Do not use anything sharp on the inside of
the rear window. If you do, you could cut or damage
the warming grid, and the repairs would not be
covered by the vehicle warranty. Do not attach a
temporary vehicle license, tape, a decal or anything
similar to the defogger grid.
Outlet Adjustment
The vehicle has air outlets on the instrument panel that
adjust the direction and amount of airflow inside the
vehicle.
Move the lever on the outlet up or down to direct the
airflow. Increase or reduce the amount of airflow by
opening and closing the louvers. The outlets can be
moved side-to-side to direct the airflow.
Operation Tips
•
Keep the hood and front air inlets free of ice, snow,
or any other obstruction (such as leaves). The
heater and defroster will work far better, reducing
the chance of fogging the inside of the windows.
•Keep the air path under the front seats clear of
objects. This helps air to circulate throughout
the vehicle.
•Adding outside equipment to the front of the
vehicle, such as hood-air deflectors, may affect the
performance of the heating and air conditioning
system. Check with your dealer/retailer before
adding equipment to the outside of the vehicle.
3-22

Blizzard Conditions
Being stuck in snow can be in a serious situation. Stay
with the vehicle unless there is help nearby. If possible,
use theRoadside Assistance Program on page 7-5.
To get help and keep everyone in the vehicle safe:
•Turn on theHazard Warning Flashers on page 3-6.
•Tie a red cloth to an outside mirror.
{CAUTION:
Snow can trap engine exhaust under the vehicle.
This may cause exhaust gases to get inside.
Engine exhaust contains carbon monoxide (CO)
which cannot be seen or smelled. It can cause
unconsciousness and even death.
If the vehicle is stuck in the snow:
•Clear away snow from around the base of
your vehicle, especially any that is blocking
the exhaust pipe.
•Check again from time to time to be sure
snow does not collect there.
CAUTION: (Continued)
CAUTION: (Continued)
•
Open a window about two inches (5 cm) on
the side of the vehicle that is away from the
wind to bring in fresh air.
•Fully open the air outlets on or under the
instrument panel.
•Adjust the Climate Control system to a setting
that circulates the air inside the vehicle and
set the fan speed to the highest setting. See
Climate Control System in the Index.
For more information about carbon monoxide, see
Engine Exhaust on page 2-45.
Snow can trap exhaust gases under your vehicle.
This can cause deadly CO (carbon monoxide) gas
to get inside. CO could overcome you and kill you.
You cannot see it or smell it, so you might not
know it is in your vehicle. Clear away snow from
around the base of your vehicle, especially any
that is blocking the exhaust.
Run the engine for short periods only as needed to
keep warm, but be careful.
To save fuel, run the engine for only short periods as
needed to warm the vehicle and then shut the engine off
and close the window most of the way to save heat.
4-18

Running Out of Fuel
If the diesel engine stalls and you think that you have
run out of fuel, do this to restart the engine:
{CAUTION:
Diesel fuel is flammable. It could start a fire if it
gets on hot engine parts. You could be burned. Do
not let too much fuel flow from the air bleed valve,
and wipe up any spilled fuel with a cloth.
1. If parked on a level surface, add at least 2 gallons
(7.6 liters) of fuel. However, if parked on a slope, up
to 5 gallons (18.9 liters) of fuel might need to be
added.2. Follow the fuel priming procedure earlier in this
section to prime the fuel filter.
3. Close the air bleed valve.
4. Turn the ignition key to START for 10 to 15 seconds
at a time until the engine starts. If the engine tries
to run, but does not run smoothly, increase the rpm
a little using the accelerator pedal. This will help
force air through the system.
The service engine soon light may come on if the
vehicle has run out of fuel. This light may stay on for a
few drive cycles after the condition is corrected, but
will eventually clear itself.
5-17

When to Inspect the Engine Air
Cleaner/Filters
For vehicle with this feature, the engine air filter life
gage will be located in the engine compartment either
on or near the air cleaner or above the switchbank in the
center of the instrument panel. It monitors the engine
air filter and indicates when the filter should be replaced.
If driving in dusty/dirty conditions, inspect the filter
each oil change.
As the filter gets dirty, the yellow indicator begins to
rise. When it reaches the red/orange change area,
replace the filter. Reset the indicator after each filter
replacement, refer toAir Filter Restriction Indicator
on page 3-46.
How to Inspect the Engine Air
Cleaner/Filter (Duramax Diesel
6.6L Engine)
{CAUTION:
Operating the engine with the air cleaner/filter off
can cause you or others to be burned. The air
cleaner not only cleans the air; it helps to stop
flames if the engine backfires. If it is not there and
the engine backfires, you could be burned. Do not
drive with it off, and be careful working on the
engine with the air cleaner/filter off.
Notice:If the air cleaner/filter is off, a backfire can
cause a damaging engine fire. And, dirt can easily get
into the engine, which will damage it. Always have
the air cleaner/filter in place when you are driving.
The engine air cleaner/filter is located in the center of
the engine compartment.
To inspect the engine air cleaner/filter, remove the filter
from the vehicle and lightly shake the filter to release
loose dust and dirt. If the filter remains caked with dirt,
a new filter is required.
5-39

Hood Inlet Seal
If the vehicle is being used in heavy snow conditions or
for snow plowing, there is a possibility of snow and
ice build up in the inlet to the air cleaner, which
can block airflow to the engine and affect impacting
engine performance.
To prevent this from happening, remove the hood
inlet seal:
1. Loosen the clamp that holds the seal to the air
cleaner.
2. Slide the seal off.3. Store the seal in the inlet, located on the underside
of the hood.
4. Store the air cleaner clamp on the coolant surge
tank. Pull the overflow tube out of the white plastic
retainer, slip the clamp over and reinstall the hose.
Replace the air cleaner seal during non-snow or non-icy
conditions.
5-41

If you get the overheat warning with no sign of steam,
try this for a minute or so:
1. In heavy traffic, let the engine idle in N (Neutral)
while stopped. If it is safe to do so, pull off the
road, shift to P (Park) or N (Neutral) and let
the engine idle.
2. Turn on your heater to full hot at the highest fan
speed and open the windows as necessary.
3. If climbing a hill, downshift to raise engine and fan
speeds.
If you no longer have the overheat warning, you can
drive. Just to be safe, drive slower for about 10 minutes.
If the warning does not come back on, you can drive
normally.
If the warning continues and you have not stopped, pull
over, stop, and park your vehicle right away.
If there is still no sign of steam, you can push down the
accelerator until the engine speed is about twice as
fast as normal idle speed for at least three minutes while
you are parked. If you still have the warning, turn off
the engine and get everyone out of the vehicle until it
cools down.
You may decide not to lift the hood but to get service
help right away.Engine Fan Noise
Your vehicle has a clutched engine cooling fan. When
the clutch is engaged, the fan spins faster to provide
more air to cool the engine. In most everyday driving
conditions, the clutch is not fully engaged. This improves
fuel economy and reduces fan noise. Under heavy
vehicle loading, trailer towing and/or high outside
temperatures, the fan speed increases when the clutch
engages. So you may hear an increase in fan noise.
This is normal and should not be mistaken as the
transmission slipping or making extra shifts. It is merely
the cooling system functioning properly. The fan will
slow down when additional cooling is not required and
the clutch disengages.
You may also hear this fan noise when you start the
engine. It will go away as the fan clutch disengages.
Power Steering Fluid
SeeScheduled Maintenance on page 6-5to determine
when to check your power steering fluid.
5-49

Four-Wheel Disc Brakes
(Hydraulic Only)
The vehicle has four-wheel disc brakes.
Some driving conditions or climates can cause a brake
squeal when the brakes are first applied or lightly
applied. This does not mean something is wrong with
the brakes.
Brake linings should always be replaced as complete
axle sets.
Four-Wheel and Six-Wheel Drum
Brakes (Air Only)
The brake drums should be removed and inspected
each time the tires are removed for rotation or changing.
When the front brakes are replaced, have the rear
brakes inspected, too.
Brake linings should always be replaced as complete
axle sets.
Brake Pedal Travel
See your dealer/retailer if the brake pedal does not
return to normal height, or if there is a rapid increase in
pedal travel. This could be a sign that brake service
might be required.
Brake Adjustment
Every brake stop, the brakes adjust for wear.
Brake Adjustment on Air Braked Vehicles
The vehicle has automatic slack adjusters. Every
brake stop, the brakes automatically adjust for wear.
Slack adjusters should never be manually adjusted
to correct excessive brake chamber pushrod stroke.
Excessive brake chamber pushrod stroke means
that the brake system needs to be serviced by a
qualified service technician.
Notice:Do not manually adjust automatic slack
adjusters. Manual adjustment of the automatic slack
adjusters can result in a degradation of the slack
adjuster performance over time. If the brake
chamber pushrod stroke is out of adjustment, the
brake system needs to be serviced by a qualified
service technician.
5-54