HVAC 26 ON VEHICLE INSPECTION (WITHOUT DISMANTLING HVAC UNIT) Since the thermistor is mounted inside HVAC unit to conduct the above test HVAC unit has to be dismantled. 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. Open the glow box & lowering Glove box lid. 3. Disconnect the Pigtail connections 4. Measure the resistance it should match to the ambient temperature. Refer graph in Inspection topic. 5. As given in the graph above (~ 5 Ohms or less for ambient temperature of 25ºC and above) 13. TRINARY PRESSURE SWITCH Trinary pressure switch is provided on the high pressure 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 Control panel in case of its intervention. The operating pressure ranges for the Trinary pressure switch is as: Pressure OFF ON DIFF Low 0.196±0.02 0.226+0.025 More than 0.02 Medium 1.47±0.15 1.96±0.12 ---------- High 3.14±0.2 (2.55) 0.59±0.2 LOCATION The pressure switch is located on the high pressure refrigerant liquid tube, besides the air filter. -0.03
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