This is a subaru forester being checked to see if 12 volts or more are being generated to the compressor. When there is no voltage, you either have a leak in the line (which is the case here), a low-pressure switch that won't allow voltage to be sent due to there not being any coolant in the system, or a bad relay. If the relays read correctly, then you have a leak or a bad compressor, a compressor clutch going bad, or a compressor clutch that needs adjusted. You can see evidence of the leak in this video where the oil is on the low-side port where the bolt is. The main video that goes through the diagnostics is here on YouTube @makeitworkdan6463