I arrived at the home because of buyers concern that the unit was not cooling properly. When I arrived that unit was off and not running. I turned both thermostat on and the unit immediately turned on. I measured refrigerant pressures and temperatures coming from the indoor unit. I can only assume that the outdoor compressor had gone into some type of safety lockout. We discussed how restricted airflow to the upstairs zone could contribute to the lockout as well as the location of the air temperature sensor. I modified the ductwork and relocate the sensor. I did also top off the unit with refrigerant. The system is now cooling with a 20° drop. And it has ran for over an hour without any issues. System is cooling properly on departure. Add refrigerant to system Relocate Discharge air temperature sensor And adjust existing ductwork to allow proper airflow to the upstairs zone It is also advised to keep the upstairs thermostat set-point 2/3° higher than downstairs because of the natur