Isuzu Amigo / Axiom / Trooper / Rodeo / VehiCross. Manual - part 1077

1A–30 HEATING, VENTILATION AND AIR CONDITIONING (HVAC)

Pressure Sensor (L4, X22SE)

The pressure sensor is installed on the upper part of the
receiver/drier. This sensor converts high pressure
detection of refrigerant to an electrical voltage signal and
supplies it to the ECM. The ECM controls switching
compressor idle speed and cooling fan operation by the
electrical voltage signal.

875R100002

Legend

(1) Pressure Switch
(2) Receiver Drier

Expansion Valve

This expansion valve is an external pressure type and it is
installed at the evaporator intake port.
The expansion valve converts the high pressure liquid
refrigerant sent from the receiver/drier to a low pressure
liquid refrigerant by forcing it through a tiny port before
sending it to the evaporator.
This type of expansion valve consists of a temperature
sensor, diaphragm, ball valve, ball seat, spring
adjustment screw, etc.
The temperature sensor contacts the evaporator outlet
pipe, and converts changes in temperature to pressure.  It
then transmits these to the top chamber of the
diaphragm.
The refrigerant pressure is transmitted to the diaphragm’s
bottom chamber through the external equalizing pressure
tube.
The ball valve is connected to the diaphragm. The
opening angle of the expansion valve is determined by
the force acting on the diaphragm and the spring
pressure.
The expansion valve regulates the flow rate of the
refrigerant. Accordingly, when a malfunction occurs to
this expansion valve, both discharge and suction
pressure decreases, resulting in insufficient cooling
capacity of the evaporator.

The calibration has been changed to match the
characteristics of HFC-134a.

874RY00019

Legend

(1) Expansion Valve
(2) Evaporator Assembly

Evaporator

The evaporator cools and dehumidifies the air before the
air enters the passenger compartment. High-pressure
liquid refrigerant flows through the expansion valve into
the low-pressure area of the evaporator. The heat in the
air passing through the evaporator core is lost to the
cooler surface of the core, thereby cooling the air.
As heat is lost between the air and the evaporator core
surface, moisture in the vehicle condenses on the outside
surface of the evaporator core and is drained off as water.
When the evaporator malfunctions, the trouble will show
up as an inadequate supply of cool air. The cause is
typically a partially plugged core due to dirt, or a
malfunctioning blower motor.

HEATING, VENTILATION AND AIR CONDITIONING (HVAC) 1A–31

The evaporator core with a laminate louver fin is a
single-sided tank type where only one tank is provided
under the core.

874RY00015

Legend

(1) Evaporator Core
(2) Expansion Valve

Electronic Thermostat

The thermostat consists of the duct sensor and
thermostat assembly which functions electrically to
reduce the noises being generated while the system is in
operation.
The electronic duct sensor is mounted at the evaporator
core outlet and senses the surface temperature of the
evaporator core. Temperature signals are input to the
thermostat unit. This information is compared by the
thermo assembly and results in the output to operate the
A/C thermostat relay and turn the magnetic clutch ON or
OFF to prevent evaporator freeze-up.

A characteristic of the sensor is that the resistance
decreases as the temperature increases and the
resistance increases as the temperature decreases.

874RY00018

Legend

(1) Duct Sensor
(2) Evaporator Core
(3) Thermostat Assembly

Refrigerant Line

Restriction in the refrigerant line will be indicated by:

1. Suction line — A restricted suction line will cause low

suction pressure at the compressor, low discharge
pressure and little or no cooling.

2. Discharge line — A restriction in the discharge line

generally will cause the discharge line to leak.

3. Liquid line — A liquid line restriction will be evidenced

by low discharge and suction pressure and
insufficient cooling.

1A–32 HEATING, VENTILATION AND AIR CONDITIONING (HVAC)

Refrigerant flexible hoses that have a low permeability to
refrigerant and moisture are used. These low
permeability hoses have a special nylon layer on the
inside.

852RS001

Legend

(1) Reinforcement Layer (Polyester)
(2) External Rubber Layer
(3) Internal Rubber Layer
(4) Resin Layer (Nylon)

HEATING, VENTILATION AND AIR CONDITIONING (HVAC) 1A–33

Air Conditioning Parts

852R100004

Legend

(1) Liquid Line (High-Pressure Pipe)
(2) Clip
(3) Discharge Line (High-Pressure Hose)
(4) Pressure Switch

(5) Receiver/Drier
(6) Condenser Assembly
(7) Compressor
(8) Suction Line (Low-Pressure Hose)
(9) Evaporator Assembly