The extruder upper fan is responsible for cooling all components of the extruder, and thus prevents the whole unit from overheating. If you notice lower quality of prints or insufficient extrusion and shortages of materials in the structure of your model, at first check the extruder upper fan for proper operation. If the fan blades don’t spin, it should be replaced with a new one. Also, the error message #140 refers to the fan’s failure. This manual shows how to carry out the replacement.
