have not been able to get my heat/cooling to work on auto on a lennox 80uhg. had the repair man out 2 times and said in was the thermostat so I replaced with a honey well rth6580wf still not working on auto. could it be the Control Board or wiring with the thermostat?

Please provide the make and model of the thermostat. Did you set it, or did the repairman? Did he do the install?