Client called about intermittent heat tech went out. WinTec arrived. Furnace was heating without issues. Tech offered to perform diagnostic client declined after hearing what has been happening from the client tech inspected thermostat. Thermostat appears to be working well tech temp. Check the temperature using a separate thermometer and both were reading the same temperature as the thermostat tech reset thermostat and inform client thermostat can be confused. If there is direct sunlight near the thermostat a heat register or electronics near the thermostat. At this time, tech does not see any issues or hear any issues with the furnace. Client declined diagnostic and asked for a quote for a wireless thermostat.