My A/C has been converted from R-12 to R-134a. The service manual gives two sets of instructions for freon, the first being to fill until the sight glass remains liquid (no foam) the second set gives graphs with pressure versus ambient temperature. I prefer the latter. The problem is that R-12 and R-134a have somewhat different charactoristics. My low pressure reading currently a bit above the setpoint, but my high pressure hoses are a bit low. Should I follow the high pressure settings since it's what the compresor is designed to put out or the low pressure settings to ensure the liquid is capable of evaporating in the evaporator?