During AMS Filament change, Unable to feed filament into the extruder

[Seong_Yun]

AMS slot assist motor stalled, due to excessive resistance in the tube near the tool head issue.

I’ve been troubleshooting an issue with my X2D/AMS 2 Pro and wanted to get some additional input.

I’m consistently getting the warning:

“Due to excessive resistance in the tube near the tool head…”

During color changes, the filament loads through the PTFE tube all the way to the printhead, but once it reaches the printhead, it doesn’t get registered on the screen. As a result, the printer backs the filament out.

Bambu Lab suggested this could be related to a left Hall sensor in the extruder head.

Something I noticed as well while troubleshooting:

When I manually straighten the PTFE tube as much as possible (reducing any angle/bends near the tool head), the printer is sometimes able to successfully detect and feed the filament.

Given this behavior:

• Could this still point to a failing or inconsistent left Hall sensor?

• Or does the improvement when straightening the PTFE tube suggest a mechanical resistance issue (tube routing, friction, alignment, etc.) instead?

Curious if anyone has seen similar symptoms or can help confirm whether I’m dealing with a sensor issue or something else.

Update (06/28 11PM): As part of my troubleshooting, I removed the PTFE tube and manually inserted a piece of filament into the extruder to verify whether the left Hall sensor was functioning.

The sensor appeared to detect the filament correctly.

So I ran another coin test print:

However, after running the test coin print again, the same issue persisted.
You can clearly see the orange filament feeding into the printhead, but the printer never registers that the filament has reached the toolhead, and it subsequently retracts the filament.

Any advice, knowledge, will be appreciated!

[dianacarver]

Based on what you’ve described, it sounds like the left Hall sensor is probably working since it successfully detects filament when you insert it manually. The fact that straightening the PTFE tube improves the loading process points more toward a mechanical resistance issue than a sensor failure.

I’d recommend checking the PTFE tube for any sharp bends, wear, or increased friction near the toolhead. It may also be worth inspecting the tube routing and ensuring the filament path is as smooth as possible. You can also get help from printestpage net which has troubleshooting guides for common printer and filament feed issues.

Hopefully that helps narrow it down. Let us know if replacing or rerouting the PTFE tube changes the behavior.

[Seong_Yun]

Hi Diana, Thank you for your feedback!

This is the back of my printer. From my perspective, I don’t see any sharp bends, what are your thoughts?

For reference, here is the response I received from Bambu Lab support:
”During the automatic feeding to the toolhead, the sensor indeed did not detect the filament. Therefore, we would be glad to arrange a new sensor for you, and we truly hope this will resolve the issue. In addition, we kindly suggest that the next time you try printing, please place the toolhead at the front of the printer to avoid resistance caused by the bending angle of the PTFE tube above the toolhead. We truly hope the issue will be resolved smoothly.”

Do you know what they mean by “placing the toolhead at the front of the printer”? Should I manually move it forward?

I’ve noticed that the issue only occurs during filament switching (when new filament is being loaded), at which point the toolhead is positioned toward the back of the printer while purging the old filament.

[CarbonForge]

I don’t know if it’s just the picture, but is the PTFE tube going from the buffer to the printer (with the yellow tape) Bambu tubing, or something else? It looks very skinny…