I performed a single heating maintenance on a 2016 carrier gas system. I checked amps, cleanliness, electrical, and safeties. Also, I cleaned the inside of the outdoor panel and resealed a duct. I discovered that the system is full of dust. The number one root cause of system failure is dust. I showed the customer videos and provided solutions to extend the life of the system. Customer stated that he would want to wait until spring to address these issues.