Just sharing this here as I’ve noticed quite a few H2S owners have run into the same issue when setting up their new machines.
Last week I bought my H2S Laser Combo and got everything set up. As soon as I tried to use the AMS and start printing, I was hit with the dreaded “high resistance feed on slot X” error on every single slot.
After spending a fair bit of time troubleshooting, here’s what I tried:
Made sure the AMS PTFE tube connecting the filament buffer to the AMS was short and free of kinks.
Triple-checked there was no obstruction or extra resistance in the tubes or buffer.
Tested different filaments, AMS slots, and spools.
Increased the PTFE tube length from 580 mm to 590 mm (and also tried 605 mm) without success. I kept it at 605 mm as 590 mm felt a bit short to me.
Tested the AMS 2 unit that came with the H2S on my X1C, and it worked perfectly.
Tested my AMS 1 unit (from the X1C) on the H2S, and it had the same issue.
Using an external spool directly worked perfectly and printed the supplied Benchy with no problems.
Tried a factory reset and full recalibration, but it made no difference.
Used different spools and filament including Bambu Lab and other manufacturers.
Firmware was already up to date.
After narrowing everything down, it turned out to be the filament buffer. I replaced it with a new one and the AMS 2 started working straight away. I did get the occasional overloaded extruder error, but that was expected as the extruder was actually being overloaded.
TL;DR: If you’re getting the “high resistance feed” error on your H2S, try replacing the filament buffer. That fixed it for me.
I’m wondering if this might be a setup detail rather than a faulty buffer in every case. Have you been able to confirm that the PTFE tubes are square-cut and fully seated in the buffer? In my experience, a tube that isn’t pushed in all the way can produce the same symptoms. That’s why I’m curious whether some H2S units are actually failing, or whether the replacement works simply because the tubes end up correctly seated.
I triple checked all PTFE tubes. Used a fresh cutter to ensure they’re properly cut and ensured they were pushed in as far as possible.
I’ve had my fair share of tinkering with 3D printers in the past with my creality printers
Additionally, I’m not saying this will be a certain fix for everyone but I hope it puts people in the right direction and would be the first thing to potentially replace as its the easiest.
Are we saying the buffers installed on H2S units come from different batches than the spare parts?
I’ve been using 3D printers since the RepRap era, so I’ve tried a lot of troubleshooting to get things printing reliably. It still feels unusual that so many H2S owners report buffer issues without a clear acknowledgment of a common cause.
I’m genuinely curious what the underlying pattern is here—whether it’s batch variability, installation tolerances, or something else.
I’d also note to double check your spools if you are getting this error. I have had a few spools with very small bends in them give me the same error. When you have more than one spool in multiple AMS units going to 2 nozzles doing this it’s hard to recognize it’s a spool issue.
I don’t think we’ll get an answer to that unless Bambu Lab acknowledge and let us know. When I created a support ticket and mentioned that I’ve checked PTFE tubes etc, their next suggestion was to replace the filament buffer.
Possibly because it’s an inexpensive part to swap.
On my H2D I can reproduce the behavior on both nozzles if the PTFE tube isn’t fully seated. In my case there’s slight resistance a few millimetres before it bottoms out; if I stop there, I get various feeding issues very similar to what you described.
If this does turn out to be a widespread issue with pre-installed buffers—it’s notable how many report problems with the stock buffer that vanish with a replacement—that would be unusual. I’m genuinely curious where the root cause is, whether in installation or manufacturing. It’s probably a mix of factors, but it is certainly puzzling.
When I first installed my H2S, it immediately and often exhibited these errors. Reading the forum here, I learned that friction in the PTFE tube might be an issue and that it can be exacerbated by tight bends in the tube.
So I cut the tube down to as short as needed to make a smooth, wide curve out of the AMS2 into the back of the machine.
i m also a new user and i get this error occasionally, i havent made any changes since i got it last week. i use the long ptfe tube that came with it and i just dont know what to do, i currently have the ams2pro sitting on top and it a roll of the dice if i get that alert. but i dont get any issues with my print so far
Just received mine yesterday and got the same error. I have 4 spools in AMS 2 and tried each one to no avail. Will reseat tube once I get home. Hope this fixes it because if I’m changing a part already right out of the box, I will be very disappointed.
