Thermistor doesnt work

Hey guys

I’ve got an issue. I replaced the thermistor of my creality 10 s pro but it doesnt work. I read that i need a ntc of 100k but the measurement reads 135k. Could this be the problem?

Can someone help me.


Its reading -15 and it isn’t I am guessing -15 in the room it is likely one of the wires is dead. I do not know the exact compatibility but I would expect if it was compatibility it would offer a reading rather than the I’m dead default.

I could be wrong.

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Those thermistor wires break very easily. Don’t reef down on them, just lightly snug.

There are different thermistor with varying resistance values if you change the thermistor type with a different resistance the setting for that type can be changed in the firmware.

Wouldn’t 135k ohms equal around 19degreesC, like room temp?

What is the temperature of the room your printer is in?

When I want to confirm the value for a thermistor, I use: NTC Thermistor Resistance Calculator V2.0
With:

  • Beta: 3950
  • Reference Resistance: 100k
  • Reference Temperature: 25C

If I plug in “18.4C” as the target temperature, the resistance calculated is 134,974 Ohms.

That doesn’t sound so unreasonable in terms of temperature (especially in January) so chances are your Thermistor is okay - but you need to confirm it by knowing the actual temperature of the room.

I learned long ago that the non-linear resistance response to temperature can be deceiving - get a cheap thermometer from a dollar store and put it by your printer.

Good luck!

myke

The room temperature was around 20°C.
So what can i do?
Im a rookie in this area…

Yeah the room temp is around 20°C.
What can i do because the printer shows -15°C…
Could it be broken?

I would say you have proven that the thermistor works at ambient.


When you say you measured 135k ohms, that was with an ohm meter, correct? I can see from your bed temp, your room was closer to 18°C which aligns with what the 135k ohms the NTC 100k thermistor would produce. -15°C would indicate your thermistor is producing around 1.618M ohms. It looks like your thermistor lead(s) is broken. Can you remove it from the hotend and unplug from your control board to do another ohm meter check? Use the chart to verify your reading at whatever temperature you are exposing the thermistor to. Also, if you think it is reading on the ohm meter properly, place it between your fingers (being polite here because there is a better place to read a body temperature), you should see the resistance drop to say 70k ohms (32°C). Lastly, if the thermistor for your bed has the same connector as your hotend, you can unplug it on the board and put it in the hotend port. You should see the hotend temp read what your bed was reading before this test. This will prove your board input is working properly.

I just read up on how to install the thermistor in the hotend, and it looks like the fixing screw should only be lightly tight, Over torqueing this screw would most likely damage your thermistor.

This is what I would try. Good luck.

Hiya,

Just an extension of what BD had wrote below.

Could you explain exactly how you are measuring the resistance across the thermistor and how it is wired into the controller?

I think we’re a bit confused that you can measure the 135k with the same wires that are going into the controller while the controller seems to be reading something different. If that’s the case, then it sounds like you could have a problem with the controller or the connector that you’re using with it.

I presume you measured 135Kohm before installing the thermistor? A simple test would be to unplug the thermistor and see what the display reads. If the display reading doesn’t change then it’s not even detecting the thermistor in the first place which implies that the thermistor leads are broken, probably inside the hot end. The glass encapsulated thermistors are notoriously fragile and as @Loosenut said, they’re easy to break during installation, so don’t tighten the nut any more than necessary.

Unplug the thermistor cable and measure the resistance of the thermistor from there. I’m betting it’s no longer 135K. Hopefully you bought a spare.