Compressor Relief Valve
WARNING: This page is about a different car, the 2002 Ford Escape. However, it is still accessible from the selected car via links, so may be relevant.
Compressor relief valve is incorporated into compressor manifold and tube assembly to relieve unusually high system discharge pressure buildups of 550 psi (38.7 kg/cm2 ) or more. Compressor relief valve prevents damage to compressor and other system components, as well as avoiding total loss of refrigerant by closing after excess pressure is relieved.