420 Benz: Your description of the location of the low pressure side Schraeder valve sounds right, but to check yourself, find the sight glass (located in same general area, in the pit behind drivers headlamp assembly). the low pressure Schraeder valve is closest to that sight glass. The high pressure valve is tucked away, not as accessible. BUT, whether obtained from Pep Boys or elsewhere, I don't think R-!2 is that easy to come by in small cans any longer. Perhaps you meant "Freeze-12," which I know is in use in the Atlanta Area for arbout $15 a can. Is the sight glass showing bubbles?