A high pressure relief valve is located on the compressor cylinder head at the rear of the A/C compressor (refer to 24 - HEATING & AIR CONDITIONING/PLUMBING/COMPRESSOR-A/C - DESCRIPTION). 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.