2017 Goodman Owner had stated the tstat would go blank and then come back on. Checked drain line and it is draining good. Found Louvers on access door to air handler and cover on AHU heavily restricted with debris. First pressure check had a 34 degree evap coil temperature. After cleaning debris out from louvers evap coil temperature was at around 50 degrees. This restriction was causing the unit to ice up and tripping AG2. Advised owner to keep louvers clean to allow proper airflow.