A/C Valves used on some '87-91 compressors. They should always be open (UNscrewed). To operate them, unscrew the black covers from the valve stems, and use a square-drive wrench to turn the stems.

Each valve's inlet is the same as its outlet, so if there's enough slack in the lines, the valves can be deleted. Their only function is to keep refrigerant in the system while the compressor is being changed. But if the compressor needs to be changed, the system needs to be evacuated, flushed, repaired, vacuumed, and professionally recharged. So the valves are actually useless.

Owner caption April 2009 · Photo 2520 of 5000