Peterbilt Model 320 Operator's Manual after 8-07 - Peterbilt Motors ...

Heating And Air Conditioning Controls
PART 4: CONTROLS AND DISPLAYS
Heating System
The heating system is a variable-coolant-flow type of system.
• Hot engine coolant is circulated by the engine water
pump through a heater core within the heater unit.
• Two blowers force air through the core and into the
cab.
The amount of heat is controlled by:
• the position of the modulating water valve that regulates
hot engine coolant flow
• the choice of fresh air or recirculated cab interior air as
feed air to the blowers
• the speed of the blowers
The system’s controls are mounted in the header in front
of the driver. They include the following (see illustration
below):
• A rotary knob to operate the modulating water valve
(for air temperature control), located in the heater control
head.
• A rotary switch to select blower speed, located in the
heater control head.
02981A
Next to the rotary knobs, two switches are available for the
following functions:
• A switch to select either fresh air or recirculated cab
air as blower feed air.
• A switch to select cab interior or defrost vents for
heated air output.
To heat the cab, select the "Cab” mode and the desired
air source, then adjust the air temperature lever and blower
speed until comfortable.
– 38 – Y53-6015 R(08/07)