K1 Filament Runout Sensor Not Pausing Print

Colin_T · December 7, 2025, 11:54am

I noticed my runout sensor was not working the other day. I figured it had broken and decided to replace it. I ended up getting the DXC Extruder which has a runout sensor in it that plugs into the hot-end pcb. After getting that all installed and doing a test print, I tested the runout function and…. nothing. It did not recognize there was no filament.

I went and factory reset the printer and still no luck.

What else could be going wrong? I would rather not have to replace the main board…

I am pretty confident I never rooted it.

Zerquetch · December 7, 2025, 10:31pm

Heya! Welcome aboard!

I’m loving that DXC extruder as well, what a great piece of gear(s), lol

There is an extra plug for it that goes into the hot end circuit board, did you do that?

If you did,The only way to enable it is to root the machine. In the Klipper settings (printer.cfg) there is a spot to enable said sensor.

Otherwise, you would need to unplug the original one and rewire it to run from the DXC

Hope it helps!

Colin_T · December 7, 2025, 11:14pm

Thanks for the welcome!

I have plugged that in to the hot end board. I ended up rooting the machine and I think I found the setting for it. But, it says it should be on. I checked the printer.cfg file and a few others that were .cfg. they all say True for pause when printer is out of filament.

I don’t have a way to wire the old one’s wiring to the new one without buying another cable I don’t think. The original one still lights up blue when in use, but the icon doesn’t show on the printer screen. Since adding the new sensor, the icon shows up very briefly on startup and then disappears.

I am concerned I will have to replace the mainboard.

Zerquetch · December 8, 2025, 3:13am

Let’s hope it doesn’t come to that!

check for 5V DC at the sensor’s connector on the toolhead PCB to confirm the port is active. The typical pinout is 5V, Ground (GND), and Signal (SIG).

On some boards you need to Invert the pin logic. Put a ! in front of the pin name in the .cfg file

But def check that the pcb is getting juice, the feature may have been turned off, so you’ll then have to call the pin in the cfg file.

Cont’d…

Zerquetch · December 8, 2025, 3:30am

IK I can be a pain, but did you follow these directions?

(Optional) Back up printer.cfg and gcode_macro.cfg
(Optional) If you want to disable the factory filament sensor, remove or comment out the [filament_switch_sensor filament_sensor_1] section in printer.cfg. To comment it out, add a # at the start of each line of the section, including the [filament_switch_sensor filament_sensor_1] line.
If a [filament_switch_sensor filament_sensor_2] section exists in printer.cfg, remove it.
Copy the following section and paste it into printer.cfg. This tells the printer that it has the DXC filament sensor connected to the filament port on the toolhead PCB, and tells it what to do when it runs out.

[filament_switch_sensor DXC]
pause_on_runout: true
switch_pin: !nozzle_mcu:PA10
event_delay: 1.5
pause_delay: 0.25
insert_gcode:
_M118 Filament inserted
_LOAD_MATERIAL # LOAD_FILAMENT IN SIMPLEAF
runout_gcode:
_M118 Out of filament
{% if printer.extruder.can_extrude|lower == ‘true’ %}
_ _G91
__G1 E-30 F180
__G1 E-50 F2000
__G90
{% endif %}

Had to use _ for spaces as the editor doesn’t like leading spaces, you get the idea

Derf · February 7, 2026, 6:50pm

Hi. Which printer does this apply to?

Alkarin · July 26, 2026, 9:26pm

Running into the exact same issue, but on a K1C 2025 (the printer.cfg header shows k1c-x2600 as the model codename — seems to be a newer hardware revision than the ones discussed above).

Confirmed the DXC sensor is plugged into the correct dedicated connector on the toolhead PCB — it’s clearly labeled “FILAMENT” on the board silkscreen, with S / 5V / G pins (photo attached).

Tried nozzle_mcu:PA10 (the pin everyone above uses) — Klipper rejects it: pin PA10 is reserved for serial. So this board revision apparently reassigned that pin.

Tried nozzle_mcu:PB0 instead — Klipper accepts it fine (no errors), but QUERY_FILAMENT_SENSOR shows “filament not detected” regardless of whether filament is actually loaded, removed, or manually pushed further into the extruder.

Has anyone with this same 2025/X2600 board revision found the correct pin for the DXC sensor on nozzle_mcu? Happy to share my full printer.cfg if useful.