When I arrived, the furnace was running. I checked the furnace out while it continued to run and found a completely clogged air filter. The air filter was causing the furnace to overheat due to the restriction of airflow. I found a lot of dirt and debris inside the ductwork. I was able to FaceTime with customer to show the air filter and ductwork. Customer would like to wait on the duct cleaning for now since customer is not in town. Customer will be back in town in a few weeks. We scheduled a return visit for March 17 12-5pm to perform a maintenance. Customer will buy a new filter and put it in ASAP.