Performed QA on NCP through the wall package unit. Reviewed installation with homeowner. Homeowner mentioned that one time the system did not seem to be running. He said he turned the main breaker off and on and the system was working again. Tested system in heating and cooling modes. Checked all wiring connections on the system. Tested the EZ trap safety on the system. Reviewed fan speed settings. Was not able to recreate that scenario again. The system worked with no issues during my visit. Did notice a line across the screen of the thermostat. Let the homeowner know it could possibly be an issue with the thermostat. He is going to monitor system. No follow up is needed at this time.