Chrysler PT Cruiser Owner's Manual page 295

If the pointer of the Coolant Temperature Gage rises to
the H (red) mark, the instrument cluster will sound a
chime. Pull over and stop the vehicle with the engine at
idle, when safe. Turn off the air conditioning and wait
until the pointer drops back into the normal range. If the
pointer remains on the H (red) mark for more than a
minute, turn the engine off immediately and call for
service.
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.
WHAT TO DO IN EMERGENCIES 293
CAUTION!
Driving with a hot cooling system could damage
your vehicle. If the coolant temperature gauge reads
"H", pull over and stop the vehicle with the engine at
idle, when safe. Turn the air conditioner off and wait
until the pointer drops back into the normal range.
After appropriate action has been taken, if the
pointer remains on the "H", turn the engine off
immediately, and call for service.
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