Printer: Creality CR-10 Smart
Slicer: Cura

My axial fan, which cools the heatsink, broke down. I replaced it with a cheap knock-off fan, as it was the only option available. However, this replacement caused temperature fluctuations that went beyond the acceptable range.

Here's what I tried to fix the issue:

  1. I initially tried flipping the direction of the axial fan to make it blow hot air instead of surrounding air. This seemed to work for a while, but it caused heat to build up, and my 3D printer's filament stopped extruding from the nozzle.

  2. I attempted to lower the current supplied to the fan, thinking it might help. However, this turned out to be a bad idea, as I wasn't sure how much current the main board could safely supply through this port. The result was that the resistor I used got fried.

  3. I then decided to mount a 740 Ω resistor in series to create a voltage drop, leaving about 10 volts for the fan. Unfortunately, this also led to heat build-up.

  4. Finally, I tried mounting a 320 Ω resistor, leaving about 14.5 volts for the fan, and this seemed to work fine.

I'm concerned about heat dissipation and the overall reliability of this solution. What are your thoughts on this?

The issue stems from the small size of the heatsink and the large size of the axial fan, which directly faces the heat block. I'm now considering the option of mounting a 24 V, 3x3 cm fan and creating a custom mount for it.

  • $\begingroup$ instead of messing around with resistors, get a cheap adjustable fan speed controller with a knob. $\endgroup$
    – dandavis
    Oct 18 at 22:00
  • $\begingroup$ not available in my area $\endgroup$ Oct 23 at 11:17

1 Answer 1


After encountering issues with an unknown brand fan overpowering the Creality fan, I experimented with resistors. Initially, a 330-ohm resistor resolved the thermal runaway warning but led to under-extrusion due to inadequate cooling.

enter image description here

A 100-ohm resistor addressed under-extrusion but triggered thermal runaway. enter image description here

The optimal solution was a 220-ohm resistor, resolving both issues. enter image description here

I've tested this setup for approximately 1 day, 11 hours, and 7 minutes with successful results.

  • $\begingroup$ why is that? the reading on the Multimeter is the voltage drop through the resistor. $\endgroup$ Nov 19 at 14:09
  • $\begingroup$ True! I misread the connections. $\endgroup$
    – Trish
    Nov 19 at 14:26

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