Arrived for no heat on gas furnace located in attic. Zone board flashing high limit open. 2 zone Honeywell system. Zone 1 12” damper. Zone 2 1-12” damper and 1-10” damper. 1-12” bypass damper. Zone 1 main level damper stuck halfway open. Return ductwork undersized at 1060 CFM not including bypass. 3.5 ton system needs 1400 CFM. High limit on zone board set at 160 F, furnace high limit is 180 F. Weak run capacitor at 7.5uf reading 6.8uf. Zone damper is open now but it will need to be replaced. Gears inside the motor are failing and will get stuck again. On the outside of the plenum connections to dampers, there are signs of biological growth. There were also signs of biological growth on the evaporator coil. Installing UV system will stop spread of any additional biological growth inside system and ductwork. Recommend adding a 10" return duct, installing flood protection, replacing weak run capacitor and replacing damper motor. Condenser coil is very dirty and needs attention before coo