Owner`s manual

183
2008 KNIGHT
ELECTRICAL SYSTEMS - CHASSIS — 9
Heater: The heater warms the air in the dash
area. Much like the refrigeration side of the
system, a liquid will be used in the process.
This liquid is the engine coolant. The coolant is
passed from the radiator to an electronic water
valve. When open, the water valve will allow
the coolant to ow through the heater core. The
heater core is much like a miniature radiator.
Air is drawn into the system by a blower motor
through the outside recirculation door opening.
Air is blown through the A/C evaporator core
and then through the heater core. When the
temperature control is in the WARM position
coolant ows through the heater core. When the
temperature is in the COOL position coolant
ow bypasses the heater core. In either position,
the airow is felt at the discharge vents.
Electric Water Valve: The water valve
controls the water ow to the heater core. A
control module compares the output voltage
from the thermostat to the feedback for the
stepper motor of the water valve. The control
module then drives the motor to within one-half
volt of the control thermostat voltage.
Functional Test:
Start and operate the engine until
the water reaches normal operating
temperature.
Set the HVAC temperature control to the
full hot position.
The discharge air outlets should have hot
air.
Rotate the temperature control to full
cold position.
Allow 10 minutes for the temperature to
stabilize.
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The discharge air outlets should have
cold air.
System Components
Compressor - The compressor is
belt driven from the engine through
the compressor and electronic clutch
pulley. The compressor will pump
freon from a low-pressure gas into a
high-pressure, high-temperature gas.
This is the start of the refrigeration
process.
Condenser - The condenser is made
of coils and ns which provide rapid
transfer of heat from the refrigerant
as external air passes over the coils.
The high-pressure gas is changed to a
high-pressure liquid.
Condenser Fan - A steady ow of
cooling air is maintained across the
condenser during system operations.
Receiver-Drier - Freon leaves the
condenser, enters the receiver-drier and
is stored until needed. The drier lters
out moisture in the system. It only
takes one drop of moisture to cause a
malfunction in the cooling unit.
 Expansion Valve - The expansion
valve suppresses the refrigerant into
the evaporator according to the cooling
requirements. The pressure is reduced
in the restrictive effort of the expansion
valve. A part of the valve is the
capillary tube assembly. The capillary
tube is the sensing bulb at the outlet of
the evaporator.
Evaporator - A tube core and ns are
used in the evaporator similar to the
condenser. Air is blown through the
ns to allow the evaporator to cool and
reduce pressure.
Blower and Motor - The evaporator
has a fan called the blower. The blower
will draw air from the cab area and
force the air over the evaporator coils
and ns. This forced air will ensure
continuous vaporizing of the R134a.
Relays and Switches - Both electronic
and vacuum switches are used in the
control and operations of the system.