Sorry for the long post. I have an ongoing support ticket with @BambuLab for 2 weeks because of faults with my printer and AMS2 Pro. I am working through the advice from Support and I am sure they will reply to me again tomorrow. They have been doing their best to help me, but I am posting here in the hope that someone has experienced this before and can just tell me what to do.
History: I switched from Low Temp filament to High Temp filament. So No.1 below may be my own fault - Or just coincidence.
But I essentially have 3 issues now:
Main Issue - Failed to Extrude Filament: I keep getting a ‘Failed to Extrude Filament’ message. This is happening across all AMS Slots. However when the filament is trying to feed, if I quickly disconnect the PTFE tube at the toolhead and manually shove the filament down approximately 10mm, I can feel it pushing into something that grips it and then it works fine, but it fails again if there is a filament change mid-print.
I have completely disassembled the toolhead (See here) down to the extruder gear and cleaned everything using a toothbrush, alcohol and washing soap. Thankyou to @L0rdS474n for the toothbrush advice.
I disassembled the AMS2 and confirmed everything is connected correctly.
I replaced all my PTFE tubes except the 4 inside the AMS2.
AMS2 Heating Issue: When following Bambu’s instructions, I disassembled the AMS2 and noticed that only one of the heaters is working (May explain PETG stringing I have been having since getting the printer). If I switch the heaters neither works on the left-side (Under Slot 1/2).
AMS2 Slot.1 Feeding Issue: I have always felt that it was more difficult to insert filament into Feeder 1 of the AMS2 compared to the other feeders. It catches sometimes and always felt like a slight grinding, even before issue.1 above. Of course this is with the tab pushed correctly while inserting it. The other feeders always felt fine. This issue seems to be getting worse as it is now grinding loudly when feeding, even though the spool rotates freely and filament is loose on it.
Issue.1 is preventing me from printing with my AMS and is really wasting a lot of filament when I try. I really thought disassembling the toolhead & cleaning was going to resolve it. Issue 2 is frustrating but I have a polymaker polydryer and an AMS-HT that I can use now that I know the heating is faulty.
I love the H2D and have been singing the praises of BambuLab since I got it in December. 2 colleagues have since bought their first 3d printers from Bambu because of my enthusiasm. I dont mind investigating issues, but its hard not to get a little tired that support keep directing me to more and more DIY documentation.
Anyway, at this point I suspect I received a faulty AMS2 and although it worked for a while, the motor is failing and no longer strong enough to push filament into the toolhead. Or perhaps my error mixing filaments caused it, but an original fault would also explain the feed issues in Slot.1 since delivery.
Does the AMS2 motor make sense as a likely cause? (Could it still be an issue inside the toolhead?) If so, I will order a replacement AMS2 motor rather than bounce around with support for another 2 weeks without any progress.
I love the printer and dont really care if the AMS was faulty originally, I just want to get it working.
From what you describe, it seems more likely that the AMS2 is the main culprit rather than the H2D toolhead.
Slot 1 has been harder to feed from day one, feels rough when inserting filament, and now makes a noticeable grinding noise, while the other slots behave better. That strongly suggests a mechanical or motor/drive issue specific to that feeder, not a general toolhead problem.
The “Failed to Extrude Filament” only occurs during material changes, and you can temporarily fix it by manually helping the filament the last few millimeters into the toolhead. Once it is past that transition, printing works until the next change. That fits very well with inconsistent feeding or positioning from the AMS2 side, rather than a permanently blocked or damaged H2D.
On top of that, one of the AMS2 heaters never gets warm, regardless of how you swap the connectors, which already confirms a hardware fault inside the AMS2.
So my working theory would be: a partially defective AMS2 (feeder 1 / motor / drive train and one heater side), possibly combined with the H2D being a bit sensitive at the hand‑off point, but not as the primary cause.
If I were in your situation, I would:
Clearly document that slot 1 has behaved abnormally from the start and now grinds under light load, while other slots are fine.
Point out that one AMS2 heater never works, even when swapping cables, which strongly indicates an internal failure of the unit, not installation error.
Ask Bambu support specifically whether they can provide a replacement AMS2 (or at least a new feeder module/motor for slot 1 plus a working heater module), instead of focusing only on the H2D.
In parallel, if you have the patience and skills to open things up, you could:
Inspect feeder 1’s gears, bearings, and filament path for misalignment, damage, or excessive wear.
Manually test feeding from another slot for a while to confirm that the H2D behaves normally when driven by a “good” feeder.
That should help you either get a proper replacement from support or confidently justify replacing the AMS2 (or its feeder/motor) yourself.
So Bambu are sending me some replacement parts for the AMS2 which will hopefully solve it. Specifically a feeder for Slot.1 and a motherboard. I have also ordered a new H2D extruder motor in case that’s the problem. Here are the results of my latest round of testing. I dont have time during the week to strip anything down, but I’ll give your suggestions for inspection a go next weekend.
Ok, so here is a summary of my latest testing:
AMS2 Pro - Any Slot - Left Nozzle: Fails to feed.
AMS 2 Pro - Any Slot- Right Nozzle: OK.
AMS 2 Pro: Failing to heat on left side.
AMS 2 Pro: Slot.1 feeder is Grinding.
AMS HT - Left nozzle: OK.
AMS HT - Right nozzle: OK.
External Spool - Left Nozzle: Fails to feed.
External Spool - Right Nozzle: OK.
Also, manually shoving the filament down when feeding is no longer getting AMS & Left Nozzle to work.
I also can’t guarantee that the issue isn’t intermittent. So some of the successful tests above could have been a fluke. I only did each 3 times.
I replaced the PCB in the AMS. The AMS heater is working now. I checked both sides with an infrared thermometer also.
However, I have now dismantled and cleaned the extruder gears in the toolhead.
I replaced the feeder in AMS Slot.1.
I replaced the AMS motor. When I replaced the AMS motor I saw that the holes for 2 of the 3 the mounting bolts were threaded. I didn’t do this, the feed issues & vibration were there before Bambu told me to take it apart.
To try to at least make some progress, I put a drop of glue into each and put the bolts back in as best I could. I figured at this point Im no worse off!
I tried a print and everything sounded smoother, but on the 1st filament change it again failed to feed to the left toolhead.
I also bought an extruder motor, but I really don’t want to strip the toolhead again unless I have some confidence its going to fix it. At this point my printer is an expensive paperweight. I was trying to be patient, but surely I can’t be expected to build a completely new system one component at a time until it works. @BambuLab haven’t even managed to tell me if its an AMS problem or a printer problem, so I dont even know if buying a new AMS would solve it. I dont know what to do.
I think I finally figured this oout.There were no idlers in the store but I figured since I was ordering them anyway, I may aswell try to take a closer look. So I started dismantling them and this tiny bit of filament somehow worked it way in there!!! Running a test print now… It wasnt visible without dismantling the left idler & popping out the little grey cap.
It wasnt visible without dismantling the left idler & popping out the little grey cap.
