Blend Air Heater and Air
Conditioner System
Constant Discharge Temperature
Control
The cab heater and air conditioner system is a Con-
stant Discharge Temperature Control (CDTC) sys-
tem. The CDTC maintains a constant temperature of
airflow in the cab regardless of outside air tempera-
ture, selected fan speed, engine coolant temperature,
or engine coolant flow. Once the temperature control
switch is turned to the desired temperature, no other
adjustments are necessary. The CDTC system is dis-
abled when the temperature control switch is in the
maximum cool or maximum warm position.
Cab Climate Control Panel
The climate control panel allows you to control the
heating and air conditioning functions of the heater
and air conditioner. See
Fig. 4.1
.
Fan Switch
The fan switch controls the fan speed and forces
fresh air or recirculated air through the selected air
outlets. The fan switch has eight fan speeds and an
off position.
To increase airflow, turn the switch clockwise or to a
higher number. To decrease the airflow, turn the
switch counterclockwise or to a lower number. Set-
ting the fan switch to the off position disables the air
conditioner and places the air source in the fresh air
mode.
NOTE: When the fan switch on the cab climate
control panel is off and the sleeper air condi-
tioner is on, the cab fan will operate at low
speed even though the cab fan switch is in the
off position. This is necessary to protect the
evaporator in the cab heater and air conditioner
system from freezing.
There is a two-second delay between the time the
engine is started and the blower is operational. It can
take an additional four seconds for the blower to
reach high speed. The blower motor performs a self-
test immediately after the engine is started, which
causes the delay.
Air Selection Switch
The air selection switch allows you to control the flow
of air through the face outlets, the floor outlets, the
defrost (windshield) outlets, or a combination of
these outlets to give you nine air selection modes.
See
Fig. 4.2
.
1.
Face Mode: Directs all airflow through the face
or instrument panel outlets.
2.
Selection between Face Mode and Bi-Level
Mode: Directs 75 percent of the airflow through
06/21/2001
f610450
1
2
3
4
O
BUNK
OVRD
1
2
3
4
5
6
1.
Bunk Override Switch
2.
Fan Switch
3.
Recirculation Button
4.
Air Selection Switch
5.
Air Conditioning Button
6.
Temperature Control Switch
Fig. 4.1, CDTC Climate Control Panel
Heater and Air Conditioner
4.1