I dont have that tool that changes them without losing the charge. But I knew the high side valve on this Honda was leaking, before it took it all apart. So I changed both schraders while it was empty. Even so....R134a is a lot cheaper than R12 ...:rolleyes::rolleyes:
Its pretty slick and SO simple.... basically a ball valve with a long stem grabber behind it. Screw the whole thing on. Turn the stem out. Close valve. Take the tool section off and swap in the new piece. Back on, Open valve, screw in the stem.