Re: Heater/AC blend doors
If a blend door is stuck in any position but closed, for sure you will get warm/hot air from the outlets which are selected. When you drive, there is some pressure buildup in front of the jeep, which can cause some airflow inside the cabin. Previously you didn´t feel it that much, since the air was cold, but with the new thermostat you will get warm/hot air even when driving in town.
If you don´t want this airflow, you could select recirculation mode. (so not sure if it stays in recirculation when the AC is switched off)