Customer states furnace was not running this morning. Furnace was running apon technician arrival. Technician cleaned flame sensor and checked all saftys. Everything is working accordingly. Customer stated back bedroom is 5 degrees warmer than the rest of the house in the winter time and colder during the summer due to imbalance airflow. Technician found that duct to far bedroom is on the very end of supply plenum causing more air to flow than the other ducts. Suggest rebuilding supply plenum and moving back bedroom duct. Furnace is running and heating the home upon departure.