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HVAC
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-0.029
+0.025
F. TRINARY PRESSURE SWITCH / PRESSURE
SENSOR
The pressure in the system is monitored by a Trinary
pressure switch. The Trinary pressure switch triggers
at 3 pressure values and sends request to Engine
EMS ECU for compressor shut OFF or to increase
radiator fan speed depending on system pressure.
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 pres-
sure reaches 0.225
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 be-
low 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 sys-
tem pressure drops below 2.25 MPa.
LOCATION: PRESSURE SENSOR (PETROL)
PIN OUT:
LOCATION: PRESSURE SWITCH (DIESEL)
The pressure switch is located on the high pressure
refrigerant liquid tube, beside the brake booster.
PIN OUT:
PIN NO
DESCRIPTION
1 -2
Middle pressure
3-4
Low and High Pressure