- 3D printers
- 3D printer
0300-0300-0001-0001
Bambu Lab 0300-0300-0001-0001 on a 3D printer: hotend fan stopped
Risk level
Medium
Proceed carefully and stop if the check is unclear.
Urgency
Medium
Quick answer
Bambu Lab HMS 0300-0300-0001-0001 means the hotend fan is spinning too slowly or has stopped. Switch off, check whether anything blocks the blades and check its connector: without that fan the filament can jam in the heatbreak.
Safety first
Stop and check this first
- Do not disable or bypass the thermal protection or change the firmware to clear the alert: it is what cuts the heat when the temperature does not add up. Do not open the printer's power supply or mains board: anything at mains voltage is for the service team.
- Bambu Lab asks you to power off the printer before touching the toolhead electronics and to use a pen or screwdriver, not your hands, to move the blades. The nozzle burns while it is hot.
Safe checks you can perform
- Nozzle at 0 °C and unplug
- Blades free of debris
- 4 pin connector and 51 °C test
- Support ticket with photo or video
Leave these tasks to a qualified professional
- Do not attempt this professional task: Reseating the FPC cable
- Do not attempt this professional task: Hotend fan replacement
- Do not attempt this professional task: TH board diagnosis
What a technician must be able to justify
Technician visit
These are the steps they must carry out and show you. Tick them as they work: if steps are skipped, do not accept a part swap.
These are not instructions for opening or handling the equipment yourself. They are the checks that should support a technical conclusion.
Reseating the FPC cable
What they doIf the connector does not fix it, the technician removes the toolhead rear cover and mid frame and reseats both ends of the FPC.
They must show youthat the FPC is fully seated.
In writingwhat was done and the test result.
Hotend fan replacement
What they doIf the fan spins freely but does not work when powered, the technician replaces it following Bambu Lab's guide.
They must show youthe 51 °C test with the new fan.
In writingthe reference fitted.
TH board diagnosis
What they doIf none of the above works, Bambu Lab says the TH board is likely faulty and asks you to contact its support for a replacement.
They must show youwhich tests ruled out fan and cables.
In writingcase number and part sent.
Before accepting a part or repair
Nothing has been shown yet. Do not accept a part swap based on the code alone.
Follow these steps
Note: Follow the documented order. An error code identifies the affected system, but it does not prove by itself which part has failed.
Nozzle at 0 °C and unplug
- Who:
- you.
- How:
- set the hotend temperature to 0 °C and disconnect the power, as Bambu Lab says before you start.
- Result that matters:
- the toolhead is cold and without power.
- If the hotend is still above 50 °C:
- the fan should keep running; wait.
- If it is cold:
- move on to the blades.
- Evidence to keep:
- photo of the screen with the alert.
Evidence: Bambu Lab Wiki: HMS_0300-0300-0001-0001: The hotend cooling fan speed is too slow or stopped
Blades free of debris
- Who:
- you.
- How:
- with the printer off, turn the blades with a pen or screwdriver, not your fingers, and remove any debris or objects.
- Result that matters:
- whether the blades turn freely.
- If there was debris:
- remove it and test again.
- If they turn freely and the alert stays:
- check the connector.
- Evidence to keep:
- photo of any debris found.
Evidence: Bambu Lab Wiki: HMS_0300-0300-0001-0001: The hotend cooling fan speed is too slow or stopped
4 pin connector and 51 °C test
- Who:
- you, if you follow the guide for your model.
- How:
- unplug and replug the fan's 4 pin connector without pulling the wires, restore power and set the hotend to 51 °C.
- Result that matters:
- whether the fan starts.
- If it starts:
- note that it was the connector.
- If it does not start:
- go to support or the technician.
- Evidence to keep:
- short video of the fan at 51 °C.
Evidence: Bambu Lab Wiki: HMS_0300-0300-0001-0001: The hotend cooling fan speed is too slow or stopped
Support ticket with photo or video
- Who:
- you.
- How:
- if the alert stays, open a technical ticket with Bambu Lab and include a photo or video of the problem and photos of the connector and the fan, together with the printer log, as the article itself asks.
- Result that matters:
- support has the code and the evidence from the first message.
- If they ask for more data:
- add the printer log and the exact model.
- If they propose a spare part:
- ask which test justifies it.
- Evidence to keep:
- ticket number, photos and video.
Evidence: Bambu Lab Wiki: HMS_0300-0300-0001-0001: The hotend cooling fan speed is too slow or stopped
Still not solved
If the error persists, stop here. See what the technician must do and show you.
Where this code applies
A code is meaningful only inside the right product and version context.
Primary scope
- System
- 3D printers
- Brand
- Bambu Lab
- Product type
- 3D printer
Known code variants
- 0300 0300 0001 0001
- Bambu Lab hotend fan too slow
- Bambu Lab ventilador hotend
- HMS_0300-0300-0001-0001
What it means
Bambu Lab explains that the hotend fan, also called the heatbreak fan, keeps the filament cool and stiff before the nozzle. If it runs slowly, the heatbreak temperature rises, the filament softens and jams inside. The printer reads the fan speed and raises the alert when it is low. The fan stops below 50 °C and starts above it. The causes it gives are blades blocked by debris such as filament strings, a badly fitted connector, a broken fan or a broken TH board.
Warnings and stop conditions
- Criticaleditorial warning
Do not disable or bypass the thermal protection or change the firmware to clear the alert: it is what cuts the heat when the temperature does not add up. Do not open the printer's power supply or mains board: anything at mains voltage is for the service team.
Evidence: Bambu Lab Wiki: HMS_0300-0300-0001-0001: The hotend cooling fan speed is too slow or stopped
- Highsource verified
Bambu Lab asks you to power off the printer before touching the toolhead electronics and to use a pen or screwdriver, not your hands, to move the blades. The nozzle burns while it is hot.
Evidence: Bambu Lab Wiki: HMS_0300-0300-0001-0001: The hotend cooling fan speed is too slow or stopped
Symptoms and causes
Probable causes · in order
- Blades blocked by debrisCommon
If filament strings or other debris block the blades, the fan cannot spin freely, and Bambu Lab lists this first.
Evidence: Bambu Lab Wiki: HMS_0300-0300-0001-0001: The hotend cooling fan speed is too slow or stopped
- Fan connector badly installedPossible
A 4 pin connector that is not fully seated or is on the wrong pin row stops the fan getting proper power or signal.
Evidence: Bambu Lab Wiki: HMS_0300-0300-0001-0001: The hotend cooling fan speed is too slow or stopped
- Broken hotend fanPossible
If the fan spins freely by hand but does not run when powered, Bambu Lab says it is likely defective.
Evidence: Bambu Lab Wiki: HMS_0300-0300-0001-0001: The hotend cooling fan speed is too slow or stopped
- Toolhead TH boardLess common
If nothing above fixes it, Bambu Lab says the TH board is likely the faulty part.
Evidence: Bambu Lab Wiki: HMS_0300-0300-0001-0001: The hotend cooling fan speed is too slow or stopped
Virtual technician
Does 0300-0300-0001-0001 still appear after these checks?
Answer a few questions to narrow down the likely cause and the safest next action. Guidance only - it never replaces a professional.
Sources and technical references
- 1
Bambu Lab Wiki: HMS Home Page, List of Error Codes for Bambu Lab 3D Printers
Bambu Lab · 2026 · official_doc
- 2
Bambu Lab Wiki: HMS_0300-0300-0001-0001: The hotend cooling fan speed is too slow or stopped
Bambu Lab · 2026 · official_doc
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