A/C Compressor Relief Valve
WARNING: This page is about a different car, the 2001 Mazda Tribute. However, it is still accessible from the selected car via links, so may be relevant.
A/C compressor relief valve is incorporated into A/C compressor manifold and tube assembly to relieve unusually high system discharge pressure build-up of 550 psi (38.7 kg/cm2 ) or more. Relief valve prevents damage to A/C compressor and other system components, as well as avoiding total loss of refrigerant by closing after excess pressure is relieved.