Was going to try and put some refrigerant in my system to check the status of my AC. Unlike most old R12 systems I've seen, both fittings are on the compressor and both have the same sized threaded fittings. Does anyone know which of the fittings is High Side vs. Low Side? The "Upper" fitting (closest to the front) has as slightly smaller line so I assume that's the low side. I can't seem to find this specific number anywhere. Anyone who has done an R-134 conversion I'd love to hear. Thanks!