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.
192 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 (H),
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.
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.
15. TOW/HAUL Indicator Light Ð If Equipped
This light will illuminate when the TOW/
HAUL button has been selected. The TOW/
HAUL button is located in the center of the
instrument panel (below the climate controls).
UNDERSTANDING YOUR INSTRUMENT PANEL 193
4

located on the control panel. Conditioned air will be
directed through the outlets selected by the mode control.
A light in the snowflake button shows that the air
conditioning is on.
Slight changes in engine speed or power may be noticed
when the air conditioning compressor is on. This is a
normal occurrence as the compressor will cycle on and
off to maintain comfort and increase fuel economy.
Automatic Temperature Control Ð If Equipped
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 surfacetemperature 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 261
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 267
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.
268 UNDERSTANDING YOUR INSTRUMENT PANEL

If you are in D (Drive) and are in 5th gear, the first tap to
the left (-) will display 5. Another tap to the left (-) will
shift the transmission into 4th gear.
On vehicles equipped with 4.7L or 5.7L engines, use of
ERS (or Tow/Haul mode) also enables a additional
underdrive gear which is not normally used during
through-gear accelerations. This additional gear im-
proves vehicle performance and cooling capability when
towing a trailer on certain grades. In ERS mode (on all
transmissions), 1st through 3rd gear are underdrive gears
and 4th gear is direct drive. ERS 5th gear (Overdrive) is
the same as the normal 4th gear.
WARNING!
Do not downshift for additional engine braking on a
slippery surface. The drive wheels could lose their
grip and the vehicle could skid.
Screen Display12345*D
Actual Gear(s)
Allowed1 1-2 1-3 1-4 1-5 1-5
* Applies to vehicles equipped with 4.7L/5.7L engines
only.
NOTE:To select the proper gear position for maximum
deceleration (engine braking), move the shift lever to the
left ªD(-)º and hold it there. The transmission will shift to
the range from which the vehicle can best be slowed
down.
Overdrive Operation
The automatic transmission includes an electronically
controlled Overdrive (5th gear for 3.7L engine, 4th and
5th gears for 4.7L and 5.7L engines). The transmission
will automatically shift from direct gear to Overdrive if
the following conditions are present:
288 STARTING AND OPERATING

Towing Tips Ð Automatic Transmission
The ªDº range can be selected when towing. However, if
frequent shifting occurs while in this range, the ºTow/
Haulº mode (if equipped) or a lower gear range should
be selected.
NOTE:Using the ºTow/Haulº mode (if equipped) or a
lower gear range while operating the vehicle under
heavy operating conditions will improve performance
and extend transmission life by reducing excessive shift-
ing and heat build up. This action will also provide better
engine braking.
The automatic transmission fluid and filter should be
changed if you REGULARLY tow a trailer for more than
45 minutes of continuous operation. Refer to the ªMain-
tenance Scheduleº in Section 8 of this manual for trans-
mission fluid change intervals.
NOTE:Check the automatic transmission fluid level
before towing.
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 N (Neutral) and increase engine idle speed.
þHighway Driving
Reduce speed.
STARTING AND OPERATING 363
5

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.)
Towing ± 2WD Models
Recreational towing is allowed ONLY if the driveshaft
is removed.Towing with the rear wheels on the ground
while the driveshaft is connected can result in severe
transmission damage.
Towing Ð Quadra-Trac I (Single-Speed Transfer
Case) 4WD Models
Recreational towing is not allowed.This model does not
have a N (Neutral) position in the transfer case.
Towing Ð Quadra±Trac II /Quadra±Drive II 4WD
Models
CAUTION!
Front or rear wheel lifts should not be used. Internal
damage to the transmission or transfer case will occur
if a front or rear wheel lift is used when recreational
towing.
NOTE:The transfer case must be in the N (Neutral)
position, and the transmission must be in the P (Park)
position for recreational towing.
364 STARTING AND OPERATING