Preformed single system heating maintenance on a 2017 heat pump. I tested all electrical components on the inside unit. All tested within manufacturer specifications. I checked for cleanliness of the system. I found the ducts to be extremely covered in dust, along with the blower wheel and the inside coil. I changed the filter for the client today 20x25x4. I proceeded outside to check the electrical components on the outside unit. All tested within manufacturer specifications. I did notice the coil to be covered in dust as well. I provided estimates to have everything addressed and cleaned. Unit was heating upon departure.