The 2009 Nissan Sentra refrigerant flows in the standard pattern, that is, through the compressor, the condenser with liquid tank, through the evaporator, and back to the compressor. The refrigerant evaporation through the evaporator coil is controlled by an externally equalized expansion valve, located inside the evaporator case. The refrigerant system is also protected by a pressure relief valve, located in the rear head of the compressor. When the refrigerant pressure in the system increases to an abnormal level [more than 3,600 kPa (36.7 kg/cm2, 522 psi)], the release port on the pressure relief valve automatically opens and releases refrigerant into the atmosphere.

The refrigerant system is protected against excessively high or low pressures by the refrigerant pressure sensor, located on the liquid tank. If the system pressure rises above or falls below the specifications, the refrigerant pressure sensor detects the pressure inside the refrigerant line and sends the voltage signal to the ECM.

The following schematic diagram shows detail flow/ cycle of the 2009 Nissan Sentra Refrigerant system. (click image to enlarge)

nissan sentra refrigerant flow diagramLegend:
1. Pressure relief valve
2. Compressor
3. Refrigerant pressure sensor
4. Condenser (with liquid tank)
5. Expansion valve
6. Evaporator
7. Front blower motor
A. High-pressure gas
B. High-pressure liquid
C. Low-pressure liquid
D. Low-pressure gas
E. Outside air

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