High Pressure Relief Valve
WARNING: This page is about a different car, the 2005 Jeep Liberty. However, it is still accessible from the selected car via links, so may be relevant.
A high pressure relief valve is located on the cylinder head of the Sanden SD-7 A/C compressor, which is at the rear of the compressor. This mechanical valve is designed to vent refrigerant from the A/C system to protect against damage to the A/C compressor and other A/C system components, caused by condenser air flow restriction or an overcharge of refrigerant.