1999 GMC JIMMY cooling

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2-9
Endgate/Liftgate
CAUTION:
It can be dangerous to drive with the rear
window, endgate or liftgate open because carbon
monoxide (CO) gas can come into your vehicle.
You can't see or smell CO. It can cause
unconsciousness and even death.
If you must drive with the rear window, endgate
or liftgate open or if electrical wiring or other
cable connections must pass through the seal
between the body and the rear window, endgate
or liftgate:

Make sure all other windows are shut.

Turn the fan on your heating or cooling
system to its highest speed with the setting on
VENT or OUTSIDE AIR. That will force
outside air into your vehicle. See ªComfort
Controlsº in the Index.

If you have air outlets on or under the
instrument panel, open them all the way.
See ªEngine Exhaustº in the Index.
Endgate Release
To open a mechanical lock system from the outside,
insert the key into the lock and turn it counterclockwise
to unlock the glass.
To open a power lock system from the outside, insert the
key into the lock button and turn counterclockwise. All
doors will unlock.
If your vehicle is equipped with the remote keyless
entry system, your vehicle does not have a lock on
the endgate. It is equipped with a pushbutton to release
the glass.
You may also use the keyless entry system, or the power
door locks, if your vehicle is so equipped.

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3-2
Comfort Controls
With this system, you can control the heating, cooling
and ventilation in your vehicle.
Standard Climate Control System
Fan Control
The knob on the left side of the heating system control
panel controls the fan speed. To increase airflow, move
the knob clockwise. To decrease airflow, move
it counterclockwise.Temperature Knob
The middle knob on the control panel lets you select the
relative temperature of the air flowing into the passenger
area of your vehicle. Move the knob clockwise toward
the red area for warmer air. Move 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.
OFF: This setting turns the system off. Some outside air
will still enter the vehicle whenever the vehicle is
moving forward.
MAX A/C: This setting provides maximum cooling
with the least amount of work. MAX A/C recirculates
much of the air inside your vehicle so it cools quickly.
This setting directs most of the air through the
instrument panel vents and a small amount through the
floor vents.
A/C: This setting cools the air entering your vehicle and
directs most of the air through the instrument panel
vents and a small amount through the floor vents.

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3-4
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
independently of the function knob setting. Move the
knob clockwise toward 82 for warmer air. Move the
knob counterclockwise toward 66 for cooler air.
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.
Choosing either maximum setting will not cause the
system to heat or cool any faster.Mode Knob - Automatic Operation
The right knob on the control panel allows you to
choose the direction of air delivery. 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.
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.

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3-6
BLEND: Airflow is divided equally between the
heater floor outlet and the windshield defroster outlets.
The air conditioning compressor may run to dehumidify
the air to prevent window fogging.
DEFROST: This setting directs most air through
the windshield defroster outlets and some through the
heater outlets. The air conditioning compressor may run
to dehumidify the air to prevent window fogging.
OUTSIDE AIR: Press this button to force the
system to use outside air. Press it 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 fresh air entering your vehicle. This is
helpful when you are trying to limit odors entering your
vehicle. In the AUTO mode, the system will use
recirculation as necessary to cool the air. Pressing the
recirculation button will change the operation to a
manual mode and the air will recirculate non
-stop. Press
this button again to turn off the recirculation feature.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: 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.
Air conditioning will be automatically disabled when
the outside temperature drops below a level which air
conditioning is ineffective.
Remember that in order for the automatic system to perform
well, it needs A/C to provide cooling performance.

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3-7 Air Conditioning
On hot days, open the windows long enough to let hot
inside air escape. This reduces the time it takes for your
vehicle to cool down. Then keep your windows closed
for the air conditioner to work its best.
For quick cool
-down on very hot days, use MAX A/C
with the temperature knob turned to the left. This setting
should be used to keep odors and/or dust from entering
the vehicle. For normal cooling on hot days, use A/C
with the temperature knob turned to the left.
On vehicles equipped with the Electronic Climate
Control system, this same performance can be achieved
as long as the A/C is enabled and the outside air button
is not active.
On cool but sunny days, use BI
-LEVEL A/C to deliver
warm air to the floor and cooler air to the instrument
panel outlets.
When the air conditioner is on, you may sometimes
notice slight changes in your vehicle's engine speed and
power. This is normal because the system is designed
to cycle the compressor on and off to keep the
desired temperature.
Heating
The heater works best if you keep your windows closed
while using it. On cold days, use HEATER with the
temperature knob turned clockwise. BLEND is useful in
cool weather when you have fog or ice on the
windshield or side windows.
If you use the optional engine coolant heater before
starting your engine, your heating system will produce
warmer air faster to heat the passenger compartment in
cold weather. See ªEngine Coolant Heaterº in the Index.
Defogging and Defrosting
On cool, humid days, use BLEND to keep the
windshield and side windows clear.
Use DEFROST to remove fog or ice from the
windshield quickly in extreme humid or cold conditions.
Turn the temperature knob to the right and move the fan
control toward high.

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3-8 Rear Window Defogger (If Equipped)
If your vehicle has this
option, the rear window
will have lines that
warm the glass.
For best results, clear the window of as much snow or
ice as possible before using the rear window defogger.
To turn on the rear window defogger, find the switch
marked REAR with the defog symbol on the lower right
corner of your climate control system. Press the button
until the light in the switch comes on, then release it. It
will only work if the ignition switch is turned to RUN.
Pressing the REAR button on your climate control
system will also activate your heated outside mirrors
(if equipped). This will help to keep ice and snow from
collecting on your mirror surfaces.The rear window defogger will stay on for five to seven
minutes, then turn off. If you need additional warming
time, turn it on again. You can turn the defogger off at
any time by pressing the button.
Do not attach a temporary vehicle license, tape or decals
across the defogger grid on the rear window.
NOTICE:
Don't use a razor blade or something else sharp
on the inside of the rear window. If you do, you
could cut or damage the warming grid, and the
repairs wouldn't be covered by your warranty.
Ventilation System
For mild outside temperatures when little heating or
cooling is needed, use VENT to direct outside air
through your vehicle. Airflow is through the instrument
panel outlets.
Your vehicle's ventilation system supplies outside air to
the inside of your vehicle when it is moving. When the
vehicle is not moving, you can get outside air to flow
through by selecting any mode and any fan speed.

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4-27 After Off-Road Driving
Remove any brush or debris that has collected on the
underbody, chassis or under the hood. These
accumulations can be a fire hazard.
After operation in mud or sand, have the brake linings
cleaned and checked. These substances can cause
glazing and uneven braking. Check the body structure,
steering, suspension, wheels, tires and exhaust system
for damage. Also, check the fuel lines and cooling
system for any leakage.
Your vehicle will require more frequent service due to
off
-road use. Refer to the Maintenance Schedule for
additional information.
Driving at Night
Night driving is more dangerous than day driving. One
reason is that some drivers are likely to be impaired
-- by
alcohol or drugs, with night vision problems, or by fatigue.

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4-35
Hill and Mountain Roads
Driving on steep hills or mountains is different from
driving in flat or rolling terrain.If you drive regularly in steep country, or if you're
planning to visit there, here are some tips that can make
your trips safer and more enjoyable. (See ªOff
-Road
Drivingº in the Index for information about d
riving off
-road.)

Keep your vehicle in good shape. Check all fluid
levels and also the brakes, tires, cooling system and
transmission. These parts can work hard on
mountain roads.

Know how to go down hills. The most important
thing to know is this: let your engine do some of the
slowing down. Shift to a lower gear when you go
down a steep or long hill.