Chevrolet 4500HD Series 2019 Manual page 133

132 Climate Controls
: Use this position to prevent
dusty or otherwise contaminated
outside air from entering the cab,
such as in a tunnel or in congested
traffic.
Extended use of the inside air
recirculation position causes the
windshield and windows to fog up
easily, making visibility poor. For
good ventilation, switch to outside
air as soon as possible.
Temperature Control Knob : Use
this knob to select the preferred cab
interior temperature. Turn the knob
counterclockwise to lower the outlet
air temperature and clockwise to
raise it.
Fan Speed Control Knob : The fan
speed can be adjusted to any of the
four speeds available.
Air Conditioning (A/C) Switch :
Press this switch to use the air
conditioning system. The indicator
light inside the switch will come on
to show that the air conditioning
system is in operation. The air
conditioning system can also be
used for dehumidifying while the
heater is being used. To turn off the
air conditioning, push this switch in
again.
When the defrost mode is selected,
the air conditioner compressor will
be on.
Even if the A/C switch is turned on,
the air conditioning system will not
operate when the fan speed control
knob is placed in the stop position.
Make sure that the fan speed
control knob is in a position other
than the stop position.
Even in seasons when the air
conditioning system is not used,
occasionally operate the system for
a few minutes with the engine
running at a low speed in order to
keep the system's components
lubricated.
Ventilation
Outside Air Ventilation : Press the
A/C switch to the off position. Turn
the outlet selector knob to the
preferred position. Move the air
selector lever to the position.
Set the temperature control knob to
the desired position. Adjust the fan
speed control knob to the preferred
speed.
How to Use the Heater
Normal Heating : Set the outlet
6
selector knob to the or
-
position. Use the position for
warming your feet while defogging
the windshield.
Set the air selector lever to the
position. Adjust the temperature
control knob and the fan speed
control knob to the desired
positions.
To dehumidify the cab interior while
heating, press the A/C switch to the
on position.
As the heater uses the heat from
the engine coolant, its heating effect
is weak when the engine coolant
temperature is low.
Maximum Heating : Turn the outlet
6
selector knob to the position, set
the air selector lever to the
-