I’m running into an H2S issue on my Bambu and can’t figure out what changed. It was working fine, then the problem started suddenly and now I need help troubleshooting the cause, possible fixes, and how to get it running normally again.
If by H2S you mean the hotend heating system or a heater fault, start with the simple stuff first.
- Check the nozzle and hotend plugs. Reseat both ends. A loose thermistor or heater plug will throw weird errors fast.
- Inspect the toolhead cable. Look for pinched spots near the chain and behind the print head. Bambu cables fail there a lot after many moves.
- Pull the sock and look for filament ooze around the heater block. Melted plastic around the thermistor gives bad temp reads.
- Run a cold tug on every connector. If one feels sloppy, that’s your suspect.
- Watch temps in the app while heating. If temp jumps 10 to 20 C instantly, thermistor issue. If temp rises slow or stalls, heater or power issue.
- Swap in a known good hotend assembly if you have one. Fastest way to split printer issue from hotend issue.
- Check part cooling fan and hotend fan. If hotend fan died, heat creep starts and things get ugly fast.
- Update firmware only if this started right after an update. If yes, note the version and search for others with the same bug.
On Bambu, the common causes are damaged toolhead cable, bad thermistor, heater cartridge, or filament blob around the hotend. Sudden failure points to wiring more than settings. If you post the exact error code, temps, and model, people can narrow it down prety quick.
If H2S is the heater system fault, I’d look one layer above what @nachtdromer listed and check whether the printer is failing only during actual print startup versus manual heating from the menu. That matters a lot.
If it heats fine sitting idle but throws H2S when a print begins, I’d suspect motion-related wiring or a fan behavior issue during the startup sequence, not just a dead heater. Bambu does a lot at once during start, so sometimes the error only shows when the head starts moving fast.
A couple things I’d try:
- do a manual preheat to your normal filament temp and let it sit 5 to 10 min
- then wiggle the harness gently while watching temp graph
- try heating with the front cover open and closed, sounds dumb but airflow/fan behavior can expose a marginal sensor
- check if the issue happens on every nozzle temp or only higher temps
- look at the startup gcode/profile changes if you edited anything recently
I kinda disagree with “update firmware only if it started after update” because sometimes a reflash fixes weird controller behavior even when the timing seems unrelated. Not first thing I’d do, but not last either.
Also, if you recently changed nozzle/hotend type in Bambu Studio and the physical hardware doesn’t match, temps can get wonky fast. Seen it happen, felt very stupid after lol.
Post the exact H2S wording and when it triggers. That narrows it down a ton.