High Pressure Relief Valve
WARNING: This page is about a different car, the 2002 Pontiac Sunfire and 2002 Chevrolet Cavalier. However, it is still accessible from the selected car via links, so may be relevant.
If the A/C refrigerant pressure sensor were to fail or if the refrigerant system becomes restricted and refrigerant pressure continues to rise, the high pressure relief valve will pop open and release refrigerant from the system. The high pressure relief valve is mounted in rear of compressor.