Pressure Relief Valve

WARNING: This page is about a different car, the 2004 Infiniti M45. However, it is still accessible from the selected car via links, so may be relevant.

The refrigerant system is also protected by a pressure relief valve, located in the rear head of the compressor. When the pressure of refrigerant in the system increases to an unusual level [more than 3,727 kPa (38 kg/cm² , 540 psi), the release port on the pressure relief valve automatically opens and releases refrigerant into the atmosphere.

Fig 1: Identifying Pressure Relief Valve & A/C Components

Courtesy of NISSAN MOTOR CO., U.S.A.