After our heater stopped working altogether last winter, we realized that it might be time to consult with a professional. We called a family friend who is also an HVAC contractor and he came out right away to see what he could do. After taking a look at things, he told us that our vents were almost completely blocked with dust and dirt. He recommended a vent cleaning company to come out and help, and they removed loads of debris the next day with specialized suction tools. After that, our HVAC system ran almost perfectly.