Arrived to do a performance maintenance. Set up for combustion analysis temperature split and static pressure tests. Verified operation of all mechanical and electronic components of the furnace. Checked blower for cleanliness and to see if there is any play in the bearings. Found that the fan for heating and cooling is coated in dust debris again. Checked systems heat exchanger to ensure proper venting of flue gas. Verified operation of the humidifier. Humidifier is in need of a humidifier panel due to it leaking. With homeowners approval scheduled a duct cleaning and blower cleaning and replaced the humidifier panel today. Relocated the moisture sensor to under the humidifier. Furnace and humidifier are operational at this time.