Challenger Terra Gator 3244 Chassis. Manual - part 105

HVAC

5-12

627333-A  

AIR CONDITIONING PROCESS

FIG. 1: Refrigerant is drawn into compressor as a

cool/cold low-pressure vapor, is compressed and then

moves out as a hot, high-pressure vapor to condenser.

As hot, high-pressure vapor passes through condenser

core, it gives off heat to cooler outside air being drawn

across condenser core by engine fan.

Hot vapor is cooled and condensed to a liquid and

moves to receiver/drier under high pressure.

Cooled high-pressure liquid is stored in receiver/drier

until it is released to evaporator by expansion valve.

Liquid refrigerant passes through a metered orifice in

expansion valve and into evaporator core. As

refrigerant passes through orifice in expansion valve,

refrigerant changes from a cooled, high-pressure liquid

to a cold, low-pressure atomized liquid. Then, when the

refrigerant reaches evaporator coils, it begins to warm

by absorbing heat from air blown across evaporator

coils and fins by blower fan.

Refrigerant now changes from a cold low-pressure

atomized liquid to a cool/cold low-pressure vapor and

leaves evaporator outlet moving back to suction

(low-pressure) side of compressor to repeat cycle.

Amount of temperature increase of atomized liquid in

evaporator is dependent on ambient/outside

temperature.

As heat loss is taking place, moisture (humidity) in air

condenses on outside of evaporator and drains off as

water through drain hoses attached to evaporator drain

pan, reducing humidity level of cab. Also, dust or pollen

not removed by cab filters collect on wet evaporator fins

and coils and are washed off with condensed moisture.

FIG. 1

LO

W PRESSURE

LIQUID

LO

W PRESSURE

VAPOR

EVAPORATOR

COMPRESSOR

EXPANSION

VALVE

CONDENSER

HIGH PRESSURE

LIQUID

HIGH PRESSURE

VAPOR

LOW SIDE

(LOW PRESSURE)

HIGH SIDE

(HIGH PRESSURE)

HEAT MOVES

FROM INSIDE AIR
TO REFRIGERANT

HEAT MOVES

FROM REFRIGERANT

TO OUTSIDE AIR

M112903002

627333-A  

5-13

HVAC

HVAC SYSTEM

FIG. 2: HVAC system is located under operator seat.

HVAC unit (1) contains components of heating,

ventilation and air conditioning systems:

•

Electronic controls

•

Cab pressurization

•

Cab airflow moisture removal (defrost)

•

Cab airflow circulation

•

Cab airflow heating

•

Cab airflow cooling

Electronic HVAC Controls

Unit is equipped with an electronic control using a

control module to provide: 

•

Automatic temperature control

•

Automatic fan control

•

LED  display

•

On-board diagnostics

•

Start-up memory

•

Display for outside air temperature

Pressurizing Cab

HVAC is used to provide positive air pressure in cab to

prevent unfiltered air from entering.

Removing Moisture from Cab Airflow

HVAC system uses air conditioning to condense

moisture in air. If necessary, air temperature can be

changed by heating system. Moisture condensed is

collected as a liquid and drained.

Circulation of Cab Airflow

HVAC needs airflow to work properly, with operator

controlling direction and amount of airflow.

Heating Cab Airflow

Air circulates by heater core to heat cab air and coolant

is circulated through core.

Cooling Cab Airflow

Air circulates by evaporator core to cool cab air.

Evaporator is cooled by refrigerant, circulated in air

conditioning system located in HVAC unit.

Air conditioning system is a closed loop circuit using

pressure changes of refrigerant to cool cab.

FIG. 2

M112703001

1

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

627333-A  

5-15

HVAC

Troubleshooting

To display diagnostics, depress key three times. Digital

display shows any active fault codes. Repeatedly

pressing key scrolls through active codes. Each code

displayed should be addressed until No Faults code E00

is displayed.

Fault Codes

For all fault codes is the possible solution check the

wiring and connectors.

No Display

•

Press control panel on key.

•

Make sure display illuminates.

•

Verify control panel is plugged into wire harness.

•

Check if wire harness is wired into vehicle properly.

No Fan

•

Turn up fan with fan up key.

•

Make sure fan is plugged into wire harness.

•

Verify circuit breakers or fuses are intact.

•

If all other functions work properly, replace electronic

control unit (ECU).

No Heat

•

Turn up heat with temperature up key. Use the

advanced diagnostics to verify that the water valve

is commanded open.

•

Inspect and verify all wiring connections.

•

Verify that any coolant shut off valves on the engine

are open.

•

Verify that warn coolant is flowing into the heater

core by testing the heater hoses.

•

Inspect and replace the electronic water valve if

necessary.

•

Inspect and replace ECU if necessary.

No Cooling

•

Turn down heat with temperature down key and

enable defrost mode. Use the advanced diagnostics

to verify that the A/C clutch is requested ON.

•

Verify that the system is fully  charged with

refrigerant.

•

Verify correct voltage is present at clutch relay on

wire harness.

•

Inspect and verify all wiring connections.

•

Inspect and replace clutch relay if necessary.

•

Inspect and replace refrigerant high pressure and/or

low pressure cut out switches if necessary.

•

Inspect compressor and clutch assembly and clutch

assembly and replace clutch if necessary.

The system is not controlling the cab temperature 

properly.

•

Inspect the Cab Air Temperature sensor.

•

Verify that the recirculation vent inlet not obstructed.

•

Inspect and replace recirculation vent air filter if

necessary.

•

Change the setpoint temperature in small

increments.

•

Verify that the water valve is working properly (see

No Heat).

•

Verify that the compressor clutch is working properly

(see No Cooling).

The evaporator core is icing up and restricting 

airflow.

•

Inspect the Evaporator Core Probe.

•

Verify that the probe is making good contact with the

evaporator fins and is not loosely inserted.

•

Reposition the probe and check the core

temperature during operation using the advanced

diagnostics.

•

Replace the evaporator core if necessary.

System is putting out cool air when heat is 

needed.

•

Reposition cab temperature sensor as required.

•

Verify compressor clutch is working properly (see

No Heat).

System is putting out hot air when cooling is 

needed.

•

Reposition cab temperature sensor as required.

•

Verify compressor clutch is working properly (See

No Cooling).

Cause

Display Reads

No Faults Detected

EO

Cab Sensor Shorted

E1

Cab Sensor Open

E2

Evap Probe Shorted

E3

Evap Probe Open

E4

Water Valve Shorted

E9

Water Valve Open

E10

No Communications w/ ECU

E17