2008 JEEP GRAND CHEROKEE cooling

of reasons, including the installation of replacement or
alternate tires or wheels on the vehicle that prevent the
TPMS from functioning properly. Always check the
TPMS malfunction telltale after replacing one or more
tires or wheels on your vehicle to ensure that the replace-
ment or alternate tires and wheels allow the TPMS to
continue to function properly.CAUTION!
The TPMS has been optimized for the original
equipment tires and wheels. TPMS pressures and
warning have been established for the tire size
equipped on your vehicle. Undesirable system opera-
tion or sensor damage may result when using re-
placement equipment that is not of the same size,
type, and/or style. After-market wheels can cause
sensor damage. Do not use aftermarket tire sealants
or balance beads if your vehicle is equipped with a
TPMS, as damage to the sensors may result.
13. Temperature Gauge
The temperature gauge shows engine coolant tempera-
ture. Any reading within the normal range indicates that
the engine cooling system is operating satisfactorily.
178 UNDERSTANDING YOUR INSTRUMENT PANEL

The gauge pointer will likely indicate a higher tempera-
ture when driving in hot weather, up mountain grades,
or when towing a trailer. It should not be allowed to
exceed the upper limits of the normal operating range.
CAUTION!
Driving with a hot engine cooling system could
damage your vehicle. If temperature gauge reads
high, pull over and stop the vehicle. Idle the vehicle
with the air conditioner turned off until the pointer
drops back into the normal range. If the pointer
remains high, and you hear continuous chimes, turn
the engine off immediately, and call for service.
WARNING!
A hot engine cooling system is dangerous. You or
others could be badly burned by steam or boiling
coolant. If you decide to look under the hood your-
self, refer to Section 7 of this manual. Follow the
warnings under ªCooling System Pressure Cap.º
14. Electronic Vehicle Information Center Display
When the appropriate conditions exist, this display
shows the Electronic Vehicle Information Center (EVIC)
messages. Refer to ªElectronic Vehicle Information Cen-
terº later in this section.
UNDERSTANDING YOUR INSTRUMENT PANEL 179
4

RADIO OPERATION AND CELLULAR PHONES
Under certain conditions, the cellular phone being On in
your vehicle can cause erratic or noisy performance from
your radio. This condition may be lessened or eliminated
by relocating the cellular phone antenna. This condition
is not harmful to the radio. If your radio performance
does not satisfactorily ªclearº by the repositioning of the
antenna, it is recommended that the radio volume be
turned down or off during cellular phone operation.
CLIMATE CONTROLS
Automatic Temperature Control
The Infrared Dual-Zone Climate Control System auto-
matically maintains the interior comfort level desired by
the driver and passenger. This is accomplished by a dual
sun-sensor in the top of the instrument panel, and an
infrared sensor located in the face of the control unit.
There are also various sensors monitored by this system
which take account for vehicle speed, A/C pressure,outside temperature, and engine cooling temperature.
The infrared sensor independently measures the surface
temperature of the driver and passenger. Based on the
sensor input, the system automatically adjusts the air
flow temperature, the air flow volume, and amount of
outside air recirculation. This maintains a comfortable
temperature even under changing conditions.
Automatic Temperature Controls
UNDERSTANDING YOUR INSTRUMENT PANEL 229
4

Air flows through the registers in the back of the
center console, and under the front seats to the rear
seat passengers. These registers can be closed to block
airflow. The center console outlets deliver conditioned
air while the floor outlets deliver heated air.
²Panel
Air flows through the outlets located in the in-
strument panel. Air flows through the registers in
the back of the center console to the rear seat passen-
gers. These registers can be closed to block airflow.
Depress this button to turn on and off the air
conditioning during manual operation only. Con-
ditioned outside air is then directed through the
outlets selected on the mode control dial. The button
includes an LED that illuminates when manual operation
is selected.
NOTE:To manually control the air conditioning the
mode selector must be moved out of the AUTO position.This button can be used to block out smoke,
odors, dust, high humidity, or if rapid cooling
is desired. The recirculation mode should only
be used temporarily. The button includes an
LED that illuminates, which indicates that the recircula-
tion mode is active. You may use this feature separately.
NOTE:Extended use of recirculation may cause the
windows to fog. If the interior of the windows begins to
fog, press the ªRecirculateº icon button to return to
outside air. Some temp./humidity conditions will cause
captured interior air to condense on windows and ham-
per visibility. For this reason, the system will not allow
ªRecirculateº to be selected while in the defrost or
defrost/floor modes. Attempting to use the recirculation
while in these modes will cause the LED in the button to
blink and then turn off.
UNDERSTANDING YOUR INSTRUMENT PANEL 235
4

Operating Tips
Window Fogging
Windows will fog on the inside when the humidity inside
the vehicle is high. This often occurs in mild or cool
temperatures when it's rainy or humid. In most cases
turning on the Air-conditioning (pressing the snowflake
button) will clear the fog. Adjust the temperature control,
air direction and blower speed to maintain comfort.
As the temperature gets colder it may be necessary to
direct air onto the windshield. Adjust the temperature
control and blower speed to maintain comfort. Higher
blower speeds will reduce fogging. Interior fogging on
the windshield can be quickly removed by selecting the
defrost mode.
Regular cleaning of the inside of the windows with a
non-filming cleaning solution (vinegar and water works
very well) will help prevent contaminates (cigarettesmoke, perfumes, etc.) from sticking to the windows.
Contaminates increase the rate of window fogging.Summer Operation
Air conditioned vehicles must be protected with a high
quality antifreeze coolant during summer to provide
proper corrosion protection and to raise the boiling point
of the coolant for protection against overheating. A 50 %
concentration is recommended. Refer to Recommended
Fluids and Genuine Parts for the proper coolant type.
When using the air conditioner in extremely heavy traffic
in hot weather especially when towing a trailer, addi-
tional engine cooling may be required. If this situation is
encountered, operate the transmission in a lower gear to
increase engine RPM, coolant flow and fan speed. When
stopped in heavy traffic, it may be necessary to shift into
N (Neutral) and depress the accelerator slightly for fast
idle operation to increase coolant flow and fan speed.
236 UNDERSTANDING YOUR INSTRUMENT PANEL

Towing Tips Ð Electronic Speed Control (If
Equipped)
þ
Don't use in hilly terrain or with heavy loads.
þWhen using the speed control, if you experience speed
drops greater than 10 mph (16 km/h), disengage until
you can get back to cruising speed.
þUse speed control in flat terrain and with light loads to
maximize fuel efficiency.
Towing Tips Ð Cooling System
To reduce potential for engine and transmission over-
heating, take the following actions:
þCity Driving
When stopped for short periods of time, put transmission
in neutral and increase engine idle speed.
þHighway Driving
Reduce speed.
þAir Conditioning
Turn off temporarily.
þrefer to Cooling System Operating information in the
Maintenance section of this manual for more informa-
tion.
RECREATIONAL TOWING (BEHIND
MOTORHOME, ETC.)
Recreational towing is not allowed.
296 STARTING AND OPERATING

IF YOUR ENGINE OVERHEATS
In any of the following situations, you can reduce the
potential for overheating by taking the appropriate ac-
tion.
²On the highways Ð Slow down.
²In city traffic Ð While stopped, put transmission in N
(Neutral), but do not increase engine idle speed.
NOTE:There are steps that you can take to slow down
an impending overheat condition. If your air conditioner
is on, turn it off. The air conditioning system adds heat to
the engine cooling system and turning off the A/C
removes this heat. You can also turn the Temperature
Control to maximum heat, the Mode Control to floor, and
the Fan Control to High. This allows the heater core to act
as a supplement to the radiator and aids in removing heat
from the engine cooling system.
CAUTION!
Driving with a hot cooling system could damage
your vehicle. If the temperature gauge reads ªHº,
pull over and stop the vehicle. Idle the vehicle with
the air conditioner turned off until the pointer drops
back into the normal range. If the pointer remains on
the ªHº, and you hear continuous chimes, turn the
engine off immediately, and call for service.
WHAT TO DO IN EMERGENCIES 299
6

NPower Steering Fluid Check..............320
NBody Lubrication.....................321
NWindshield Wiper Blades................322
NWindshield Washers Ð Front And Rear.....322
NExhaust System......................323
NCooling System.......................324
NHoses And Vacuum/Vapor Harnesses.......329
NBrake System........................329
NBrake Fluid Level Check................331
NFuel System Hoses....................332
NAutomatic Transmission................333
NFront And Rear Wheel Bearings...........333NAppearance Care And Protection From
Corrosion...........................333
mFuse Panel...........................338
NInterior Fuses........................338
NUnderhood Fuses (Power Distribution
Center)............................341
NUnderhood Fuses (Integrated Power
Module)............................344
mVehicle Storage........................345
mReplacement Bulbs......................346
mBulb Replacement......................347
NHigh Intensity Discharge Headlights (HID) Ð
If Equipped.........................347
NHead Light..........................347
304 MAINTAINING YOUR VEHICLE