Return visit ac is not cooling again. Turned on the thermostat then dropped the temperature to 65f, found low batteries displaying on the thermostat, replaced 2 double A batteries then inspected the indoor system, found system very low in refrigerant, performed electronic leak search and found a refrigerant leak on the outdoor system, brazed the leak then pulled vacuum, recharge the system with 7 lbs of R 410a then cycled the syste. Job complete