If your Bambu AMS starts producing extra stringing, popping, rough top surfaces, or inconsistent layer quality even though the printer was fine last week, do not blame the machine first. A lot of "mystery AMS problems" are just moisture problems wearing a different costume.
The trap is simple: people assume the AMS is a dryer. It is not. It is a storage-and-feeding system that works better when the spools going in are already in decent shape and when the humidity-control parts inside the unit have not been ignored for weeks or months.
If your AMS prints are suddenly acting like the filament is wet, the most useful fix path is usually this: check the real humidity, refresh the desiccant, and dry the actual spool if it is already loaded with moisture.
The short answer
If you want the most practical product fixes for this problem, start with the Govee Mini Hygrometer Thermometer so you can stop guessing, replace tired inserts with the AMS Compatible Desiccant Cartridges 12-Pack, and if the spool is already wet, move it to a real dryer like the SUNLU Filament Dryer S4 because the AMS will not reverse absorbed moisture on its own.
What wet-filament symptoms in an AMS usually look like
- more stringing than usual even after you re-run the same profile
- tiny pops, hiss, or steam-like behavior during extrusion
- rougher walls or top surfaces on materials that were printing cleanly before
- brittle support material or inconsistent support breakaway
- PETG, TPU, nylon, or similar spools acting worse after sitting loaded for too long
Those are all signs that the problem may be the spool condition or the humidity environment around it, not some sudden magical failure in the printer.
What to change first
1. Stop guessing and measure the humidity
This is where the Govee Mini Hygrometer Thermometer earns its keep. A lot of AMS owners say they are "pretty sure" their setup is dry, but they do not actually know what the environment looks like in the cabinet, bench area, or storage box feeding the system. If the room, enclosure area, or nearby storage lane has drifted upward, the loaded spools can keep picking up moisture faster than you think.
- best first buy if you keep troubleshooting by feel instead of by data
- useful for AMS-adjacent storage boxes and bench cabinets too
- cheap compared with wasting time retuning prints that are actually moisture-limited
2. Refresh the desiccant before you call the AMS "bad at humidity"
If the spools are staying loaded in the AMS for long stretches, old desiccant becomes the obvious failure point. The AMS Compatible Desiccant Cartridges 12-Pack is the simple maintenance fix here. This is not glamorous gear, but it directly addresses one of the most common reasons an AMS slowly gets worse without any obvious hardware change.
- best fit if your AMS was fine earlier and gradually got less reliable
- good low-cost move before buying bigger hardware
- especially useful when PETG, TPU, or nylon live in the AMS longer than they should
3. If the spool is already wet, move it to a real dryer
This is the step a lot of people skip. Fresh desiccant can help maintain a spool. It does not magically pull serious absorbed moisture back out of nylon, PETG, TPU, or other damp material in a hurry. If the filament is already compromised, the SUNLU Filament Dryer S4 is the more honest fix because it actually dries the spool instead of just storing it in a somewhat better environment afterward.
- best move when the symptoms are already obvious in the print
- stronger answer for wetter materials and busier multi-spool benches
- better than pretending the AMS alone can recover a bad spool
When each fix makes the most sense
Buy the Govee first if you do not have real humidity visibility
If you cannot answer "how humid is this storage setup actually getting?" then measurement is the smartest first step. Troubleshooting gets a lot easier once you stop using vibes as instrumentation.
Buy the AMS desiccant cartridges first if the system simply has not been maintained
If your AMS has been loaded for a while and you have not refreshed the humidity-control side of it, this is the lowest-cost and most directly relevant first move.
Buy the SUNLU S4 if the spool already prints wet
If the material is already stringing, popping, or leaving ugly surfaces, maintenance alone is usually too late. At that point you need drying, not optimism.
What this article is not saying
Not every AMS issue is moisture. PTFE drag, worn feed paths, bad spool winding, and hub problems can also cause ugly behavior. But when the print symptoms look like classic wet filament, starting with a humidity check and a maintenance reset is a lot smarter than immediately tearing into the machine.
Editorial take
If I were fixing this on my own bench, I would do it in the same order I would diagnose any repeatable shop problem: measure first, refresh the cheap maintenance item second, and only then escalate to a real dryer if the spool is already compromised. That is why the Govee plus AMS desiccant combo makes sense as the first troubleshooting lane, while the SUNLU S4 is the better recovery tool once the material has already gone off the rails.
Bottom line
If your Bambu AMS still prints like the filament is wet, start with the Govee Mini Hygrometer Thermometer so you know the real humidity, replace tired inserts with the AMS Compatible Desiccant Cartridges 12-Pack, and if the spool is already in bad shape, dry it for real with the SUNLU Filament Dryer S4.