Hotend cooling fan not turning on when heating extruder


I have a problem with the fan of my hot end (not the fan for filament cooling). Although the firmware is configured correctly in my opinion, the fan does not start when the fan heats up, but remains off.

The fan runs with 12V on my RUMBA board at fan pin 2 (there are only 2 fan pins). If you enter "M106 P1 S255", the fan starts without any problems.

What could be the reason?

Here's the configuration.h:


  • Normally this fan is connected to permanent 12 volt so it is on all the time.
  • That you have defined it as second filament cooling fan. What you want is an extruder cooler, so remove this second fan option and in extruder definition set fan2 as cooler fan pin. Then it turns on as soon as it gets hotter then 50°C or heating is on.
  • Thank you.

    Yes, I confused the second cooling fan with the extruder cooling fan. Maybe you want to rename the entries in the FW configurator? I think it's a bit misleading.

    Maybe you want to rename

    Fan pin for first print cooling fan
    Fan pin for second print cooling fan
    or so?
  • Another question:

    Cooler PWM speed / EXT0_EXTRUDER_COOLER_SPEED is the setting for controlling the speed of the extruder cooler, isn't it? My problem is the fan runs with max speed though I set the PWM to 128 (half speed).

  • Yes that is the right value, but it also copied into eeprom and I guess you have 255 in eeprom. Just chenge it in eeprom.
  • I believe there is an issue with the online configuration tool 1.0.0 when uploading your current configuration.h file.  The online configuration tool does not take into account your current setting for the extruder cooling fan.  This issue is repeatable.  I have the EXT0_EXTRUDER_COOLER_PIN set correctly in my current configuration.h to HEATER_2_PIN when the file is uploaded but the value displayed in the drop down box resets to "Disabled / No Pin Defined".  If the value in this drop down box is not changed to the correct value, the new configuration.h that is downloaded has this value set to -1.  If I reselect the correct value of HEATER 2, then the downloaded file is correct.
  • Did you change manually in configuration.h to set the value? Such changes are NEVER seen by config tool. Config tool only reads the json string in the comment at the end of the configuration.h. So you always need to make changes in config tool and then download.
  • Ok, got it.  Thanks for the information.  It is working now

  • Hi, I want to connect an extruder cooling fan on the 12V aux connector on Ramps 1.4 (left of the X steppercontroler).
    I use the Aduino Mega 2560 with the Ramps 1.4. in my 3D-printer.

    How can I define this Extruder 0 cooling Fan in the config tool? 
    What is the pinnumber for the 12V Aux connector?

    The picture show the testboard with stepper and fan.

    In Repetier-Firmware Configuration tool I set Extruder cooler pin to Fan2 pin but it give an error message
    Error message: 'DIOORIG_FAN2_PIN_DDR' was not declared in this scope


    Thank you.
  • Ramps has only one output for a fan (ORIG_FAN_PIN ->D9) which is also used for second extruder heater. If you use a extender check to see what the pin number is.
  • Thank you for your answer.
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