Sam J - arrived to customer with no heat on upflow furnace in garage. Spoke with customer and she had gotten home from work with no heat and unit set at 72, reading 59 inside. Began checking coil and heat exchanger which are both clean, system is only 2 years old. Also checked the filter and found very dirty filter, which wasn’t allowing any air through. Cycled power to the system after recording fault code and checked operation. System began heating properly and I allowed system to,run for several minutes while I spoke with customer about the benefits of Interstate Memberships. System is operating properly and efficiently at this time. Informed customer about filter location and requirements for future reference.