HEXA

HVAC 24 -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. 4. 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: