Hello, 
I have not used my 3D printer K8200 for a long time. Now when I connect my 3D printer, I always get this error message (attached). After that the extruder does not heat up any more and the error message appears again and again. Sometimes it appears immediately after connecting or then when starting printing. I have already checked if everything is connected correctly. I could find no fault. I also checked the thermistor NTC 100K. I have no idea what the mistake is anymore.
Thanks for the help 
Hello Ever,
This error indicates that there is something wrong with the thermistor.
Thermistor defective. Or either a problem with thermistor wiring (wires).
=> False contact, false contact on “therm” connector mainboard.
Regards,
Velleman support