A dirty or clogged filter is the most common cause of furnace problems, as dust and dirt restrict proper airflow. When a filter gets clogged, the heat exchanger can overheat and shut off too quickly. The result is a cooler temperature in your home than the one you set on the thermostat. Other reasons for uneven heat in your Beaufort home include a faulty thermostat and blocked vents and ducts, which also restrict airflow.