I have problem with my K1C that big tension in extruder cut PLA filament in every print. Have anyone the same problem? How can I repair it easily?
Is the filament wound too tight on the reel? Read about some finding this. Is the filament properly dry? It breaks easily when wet it also breaks easily if it is exposed to UV. How do you store the filament?
I’m with Bonfireman here, the tension is coming from farther down the line. I’ve had the filament get crossed a couple of times and no longer feed. When that happens it usually just flattens the filament in the extruder feed wheels and I have to take it apart to clear it out. Once it’s deformed inside the extruder, it won’t go either way on the K1C, so it’s disassembly time.
Never let go of the end of the filament. Do not let anyone else handle your filament. This is sacrosanct. One of the ten commandments of the 3D printing bible. Tangles come from users not the factory. A gleeful post from the Anglo Saxon Spear.
Yep, one of the first times I changed filament in my printer I let the end get away, first jam! Now I put the spool on, grab the filament and then cut it at the holding holes. After I stuff it in the bowden tube so it can’t unspool, then I just cut the end out of the retaining holes.
I also dry the filament when I pull it off to change it, then put it in a ziplock bag with a few fresh silica gel baggies. An investment in a $50 dryer is a good investment IMO. I bought the indicator bags of silica gel so I could tell when I needed to recharge them. However, when I unpack a filament, I always put the silica gen in the “expired” bag to be baked, I never try to use it twice.
6 printers all have dryers, I live by the sea, near a stream and woodland, rather wet. Definitely need dryers. Oh to live in a desert.
I dried my filament before my print yesterday. So here is no problem with wet filament.
Top suspect is it getting tangled on the reel I would think. It just takes one crossed turn on top of the feed to cause a jam. Been there, done that, it sure did screw up the works!
What everyone else said so far. 
In addition I would start by disconnecting the bowden tube at the extruder and pull the filament through to see if the resistance is back towards the runout sensor.
If it pulls through smoothly you’ll probable need to disassemble the extruder and check gears.