dodge guy wrote:
A good AC guy knows how to read gauges (and I am one of those people). You have to know outside temp and humidity and have a chart to compare that to the pressures on your gauges as well as the vent outlet temperature. It can be done with the right person. Sadly not many like that left anymore!
Another trick is to put you hand on the low side line just as it leaves the evaporator and feel the cold. As you add refrigerant you will feel the line getting colder. Then you will feel a cold rush of about a 10 degree drop. That's the point when the evaporator is boiling refrigerant through it's entirety. Add 4 more oz. to make sure you have a good liquid seal on the receiver/dryer down tube and you'll be nuts on.
Richard