Artillery Ruby V1.2 hotend cooling fan

General Discussion
1

Basic Information:

Printer Model:
MCU / Printerboard:
Host / SBC
klippy.log

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Describe your issue:

…Hi,

I’m having an issue with the heater_fan on my Artillery Hornet 3D printer running Klipper firmware with an Artillery Ruby V1.2 mainboard (STM32F401).

Problem:
The

printer.cfg (13.1 KB)

hotend cooling fan (PC7 pin) does not run at full speed when controlled by the heater_fan module. Instead of running at 100%, it runs at approximately 60% speed and fluctuates/pulses continuously. This is causing heat creep in the heat break and potential clogs.

Key observations:

  1. When Klipper restarts, the fan immediately spins at 100% (before Klipper takes control)
  2. Once Klipper’s heater_fan callback takes over, the fan drops to ~60% and fluctuates
  3. When I send M106 S255 manually, the part cooling fan (PC8) spins at 100% - this confirms the hardware is working correctly
  4. The fan audibly moves less air when controlled by heater_fan vs when Klipper first starts
  5. This issue started after recent Klipper updates

What I’ve tried:

  • Adding fan_speed: 1.0
  • Adding kick_start_time: 0 and kick_start_time: 0.5
  • Adding max_power: 1.0
  • Adding off_below: 0.2
  • Adding shutdown_speed: 1.0
  • Adding cycle_time: 0.00004
  • Reverting heater_fan.py to original Klipper code
  • Clearing .pyc cache files

None of these changes made any difference.

Current config:

[heater_fan hotend_fan]
pin: PC7
heater: extruder
heater_temp: 50.0

Mainboard: Artillery Ruby V1.2 (STM32F401)
Klipper version: Latest (master branch, 351+ commits since October 2025)

It seems like the heater_fan module is sending the correct speed value (1.0) but something in the PWM signal chain is limiting the actual output to ~60%. The fan runs at full speed before Klipper takes control, which suggests this is a software issue introduced in a recent update.

Has anyone else experienced this with the Artillery Ruby V1.2 board? Any suggestions would be greatly appreciated.

Thank you!

2

Please attach the requested klippy.log to your next post.

3

klippy.log (3.6 MB)