Challenger Terra Gator 3244 Chassis. Manual - part 107

HVAC

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Temperature in Cab

Temperature of inside cab airflow is measured by

temperature sensor in HVAC unit. Cab airflow is drawn

through recirculation filter and passed sensor.

Outside Temperature

Outside temperature is measured by sensor located

near drive motor for rear window wiper.

Temperature of Ventilation Duct

Temperature of cooled or heated air in ventilation duct

is measured by a sensor (5) located in blower fan

housing.

Probe for Evaporator Coil

FIG. 11: Probe (1) is inserted into evaporator coil to

monitor temperature. Probe limits control signal of

clutch for refrigerant compressor. Control signal for

clutch is interrupted when temperature of evaporator

coil is below 0 °C (32 °F), preventing evaporator coil

from freezing. Moisture in airflow condenses and

freezes below 0 °C (32 °F). Frozen moisture inhibits

airflow through evaporator coil.

If the air flow coming out of the vents gates is about 7°C

/ 8°C (44,6°F /  46,4°F). The airco is working good.

FIG. 11

M121103006

1

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HVAC

EVAPORATOR COIL

FIG. 12: Evaporator Operation

Evaporator (1) is located in HVAC unit in front of heater

coil.

Evaporator transfers heat in cab to refrigerant.

Evaporator receives liquid refrigerant, with low pressure

and temperature. Since pressure of liquid refrigerant is

low, temperature of saturation of refrigerant is low. As

temperature of saturation changes, refrigerant changes

from liquid to vapor.

Blower fan exposes evaporator coil to air inside cab.

Heat from air inside cab is absorbed by evaporator

transferring heat to refrigerant, at which time it reaches

temperature of saturation and changes from a liquid to

a vapor. The amount of heat required to reach

temperature of saturation is called latent heat of

vaporization. Vaporized refrigerant leaves evaporator

and carries heat away from cab. Vaporized refrigerant

returns to compressor when refrigerant leaves

evaporator. This process is repeated continuously.

Temperature of evaporator coil is monitored by a

temperature sensor inserted into evaporator coil.

See Systems Operation/Testing and Adjusting,

Temperature Sensors for additional information.

HEATER CORE (CAB)

FIG. 13: Heater core (1) is located in HVAC unit.

Airflow is forced past heater core to gain heat from

engine coolant. Engine coolant is circulated through

heater core. Airflow is created by blower fan in HVAC

unit.

Heater core is constructed of copper and aluminum as

these metals are excellent heat conductors. Heater

core and water valve are connected with a heater hose.

These connections are critical and should be checked

periodically for leaks.

FIG. 12

1

M121103010

FIG. 13

1

M121103010

HVAC

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ACTUATOR MOTOR (WATER VALVE)

FIG. 14: Water Valve with Actuator Motor

Water valve (1) controls amount of water flowing into

heater core. Foreign matter on outside surface of

heater core can cause a poor exchange of heat.

Heating system loses capability to heat when heater

core gets dirty. Clean outside surface of heater core

when system is checked.

Valve actuator is used to control water valve with

sixteen positions available and is dependent on amount

of heat required. Position of water valve changes as

selected temperature changes. A potentiometer

detects position of water valve and feeds information

back to control module.

FIG. 15: Water Valve Schematic

Inside actuator (A)

6-Pin Actuator (B)

FIG. 14

1

M12110315

FIG. 15

N011803003

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HVAC

AIRFLOW

Components for Airflow

Airflow Components

HVAC Unit

Air Filter (Fresh Air)

Air Filter (Recirculation)

Damper Control (Deluxe Cab)

Inlet for Recirculated Air

Inlet for Fresh Air

Blower Fan

Sealing Area

Blower Fan

FIG. 16: Internal components with rear cover removed

Blower (1) is located in HVAC unit and has:

•

Inlet for fresh air and inlet for recirculated air.

•

Outlet for vents on left side of the cab.

•

Outlet for vents on front console.

•

Outlet for vents on right side of cab.

Motor drives blower.

Intake For Airflow

HVAC unit draws air from fresh air inlet and recirculates

in cab. HVAC unit is designed to draw 20% fresh air

from outside and 80% interior air, this is not adjustable.

FIG. 16

M12110311

1