I arrived at our clients home to replaced the failed schrader valve. Before I began I gave Tim the option to completely remove the refrigerant and weigh in a fresh charge or attempt to top it off under the current weather conditions. With the understanding that we may have to return when it is warmer to add additional refrigerant if needed. He elected to add refrigerant to the current amount and monitor the systems performance. Once I replaced the schrader valve I tested it to ensure it wasn’t leaking. I then proceeded to add refrigerant and test the systems cooling capacity. I gradually added Freon and measured the system performance until I added a little over 3lbs of Freon. The system is cooling with a 18° delta T from outdoor ambient temp. Did shut the unit off upon departure.