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What problem are you having? Do you have a sight glass on your low side connection usually near the dryer. When filling with refrigerant, you fill till the bubbling stops in the sight glass. Usually the high and low side pressure vary depending on load and outside and inside air temps. Most gages have a range for each type of refrigerant. The low side connections should sweat but not freeze on the outside. The rear AC evap coil tubes tend to have holes rubbed in them.