Service Manual

Table Of Contents
5-14 627333-A
HVAC
AUTOMATIC TEMPERATURE CONTROL
Description
The Automatic Temperature Control (ATC) allows for
true interior cab temperature control and continuously
variable blower fan speed through the use of advanced
microprocessor and sensor technology.
1. ON / OFF - Powers vehicle Heater-A/C control
system on or off. The LED numeric display is
illuminated when the unit is turned on. The display
will show the current set point temperature.
2. AUTO - Places the system in a fully automatic
temperature control mode including automatic fan
speed control. A panel light indicates when this
mode is active. The system will adjust the blower
fan speed to the lowest setting necessary to
maintain the cab temperature at the displayed set
point temperature.
3. DEF (Defrost icon) - Energizes the A/C system to
allow for rapid de-humidification of the cab. The A/C
will be enabled even if the set point temperature
requires heat. A panel light indicates when this
modes is active.
4. FAN UP / DOWN - Overrides the automatic fan
speed control feature. Increments fan speed up or
down in eleven steps. The digital display indicates
the fan speed setting as a percentage or “HI” when
maximum fan speed is reached or “LO” when
minimum fan speed is reached then returns to
normal display five seconds after either key is
depressed. The set point fan speed is maintained
until it is changed or if the AUTO key is depressed.
5. TEMPERATURE UP / DOWN - Increments the set
point temperature up or down. The system will
control the electronic water valve and/or the A/C
compressor clutch to hold the cab temperature as
closely as possible to set point temperature.
6. ECON (Economy Mode) - When depressed, locks
out the A/C function. The control uses only fresh air,
fan speed, and water valve control to maintain the
set point temperature. Depressing the ECON key
will return the system back to normal operation. A
panel light indicates when this mode is active.
7. C / F - Switch between Fahrenheit and Celsius.
FIG. 3
1
2
3
6
7
4
5
Climate Control
4
5