1. Preheat the nozzle to 230 degree, press the edge of the quick fitting and pull the white guide tube out. removing the quick fitting with a M10 spanner, penetrate the nozzle by using a 1.5 mm hexagonal wrench, keep cleaning until the defective filament come out of the nozzle.
2. Clean the nozzle with new filament, until the filament come out of the nozzle.
3. Install the quick fitting, remove the guide tube from the extruder, cleaning the defective filament in guide tube.
4. Feed the new filament through out the guide tube until it can seen from the other side, pull it out and install all the parts been disassembled.
Here is the link of the video: https://www.youtube.com/watch?v=s74gs_hKvq4&t=86s