HEXA

HVAC

-0.029

ON VEHICLE INSPECTION

(WITHOUT DISMAN-

TLING HVAC UNIT)

Since the thermister is mounted inside HVAC unit to

conduct the above test HVAC unit has to be disman-

tled.

Alternatively following test can be conducted without

dismantling the HVAC unit:

1. Switch OFF the HVAC unit and allow the HVAC

unit to come to ambient temperature.

2. Disconnect the Pigtail connection.

3. Measure the resistance it should match to the

ambient temperature. Refer graph in Inspection

topic.

As given in the graph above

(~ 5 Ohms or less for

ambient temperature of 25ºC and above.)

G. TRINARY PRESSURE SWITCH

Trinary pressure switch is provided on the high pres-

sure tube liquid line of the refrigerant and it is

functionally connected to engine EMS to control the

AC compressor and radiator/ condenser fan through

the Engine EMS. It also gives a feedback to the Con-

trol panel in case of its intervention.

It has the following three functions:

1. Low Pressure Shut OFF: When the pressure

drops below 0.196 ± 0.02 MPa, indicating a

leakage, the compressor is shut OFF. It

switches ON the compressor again after the

system pressure reaches 0.225

+0.025

2. Middle Pressure detection: When the system

pressure reaches 2.01 ± 0.1 MPa it requests

Engine EMS to run the radiator/ condenser fan

at a higher speed. When the pressure drops

below 1.52 ± 0.15 MPa the fan is requested to

run at normal speed.

3. High pressure shut OFF: When the pressure

rises above 3.14 ± 0.2 MPa, indicating a pres-

sure build up, the compressor is shut OFF. It

switches ON the compressor again after the

system pressure drops below 2.25 MPa.

LOCATION: