FIXED Nozzle Temperature dropping and fluctuating rapidly

Anycubic_Kossel_Plus Failed_Print temperature thermal_runaway

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Just recently, my nozzle temps have been extremely unstable. Whenever I start a print, the recently stable 200 degrees Celsius drops drastically - by around 15 degrees. This almost always triggers thermal runaway. However, if it doesn't, the temperature fluctuates rapidly by around 7 degrees during the print.

I've already calibrated the PID, and even tried to use auto temp.

Could anyone help fix this? Thanks in advance.


I replaced the heater cartridge and now the temperatures are stable. Thank you all for replying!

Same thing... Im just change the heater and all is good again...

As said, check thermistor, and heater cartridge. Also make sure the cabling of the heater cartridge is seated properly (cables / connectors might be charred if not connected well enough).

Thanks for the reply, you are right, I checked the thermistor, connections, and eventually replaced my heater cartridge, which fixed my issue.

It's not possible for the heater block to change temperatures super quickly; it has a reasonable amount of thermal inertia. If by "drops drastically" and "fluctuates rapidly" you mean changes over the course of a couple of seconds, that strongly suggests the problem is actually with sensing the temperature. Maybe the thermistor isn't fully seated in the heater block, or the wires to it are loose or worn, or there's dirt or corrosion on a connector for it, etc.

I set nozzle temp at 200 and tested the heater block with a temperature probe that I know works. The thermistor and probe both displayed 200.

Hi Joanna1234.

I think it possible that your heater cartridge is on the point of failure. I had similar symptoms some time ago and cured the problem by fitting a new heater cartridge (I also used Kryonaut thermal grease from thermal grizzly to couple it, and the thermistor, to the heater block). It could also be broken wires or loose connectors on your heater or thermistor.

Please post here with whatever fixes your problem.

Thanks for the help, I replaced my heater cartridge and it fixed my issues.

Excellent. Thanks for posting your solution. Happy printing.