¶ What it is
There is a speed feedback signal from the hotend fan. The hotend fan (or called heatbreak fan) is used to keep the filament outside the nozzle cool and solidify. If the hotend fan speed keeps low, then the hotend heatsink temperature will rise and cause the filament to soft and then jam inside the heatbreak.
Below are the possible reasons:
- The fan blade is stuck by something ( like filament ) and cannot spin freely
- Poor contact between the hotend fan and the TH mainboard connection
- The fan is faulty
- The TH board is faulty
¶ Safety warning and Machine state before starting operation
When cleaning the fan, the fan may start spinning suddenly and cause injury. But as there is no switch that can turn on/off the hotend fan, using a pen or screwdriver to do the following steps is recommended.
¶ Troubleshooting guide
¶ Step 1
Set the hotend temperature to 0 °C. When the hotend temperature drops below 50°C, the hotend fan will automatically shut down (the fan turns on automatically when the hotend reaches 50°C and turns off automatically when it falls below 50°C).
¶ Step 2
Take off the front cover, and use a pen or a screwdriver to spin the fan blade, to see if the fan blade was stuck by something. If yes, please remove it.
¶ Step 3
After cleaning up the mess, reconnect the 4-PIN connector on the hotend fan. Set the hotend temperature to 51°C. The hotend fan will start running again (if it is not stuck or broken) and see if this HMS message disappears.
If have a P1P printer, please be careful not to plug the hotend fan in the wrong way.
 Correct installation |
 Incorrect installation |
¶ Step 4
If you have a spare hotend fan or a complete hotend assembly (with the fan), you can replace it with a new fan to see if it can fix the problem.
Pay attention to the installation direction of the hotend fan. Reverse installation may cause errors, abnormal hotend fan speed or frequent plugging.
- Correct installation：
 |
 |
- Incorrect installation：
 |
 |
¶ Step 5
If you still can't solve this problem. It is recommended that you re-plug the 10-pin connector. And check whether there is any sign of damage on the 10-pin plug.
If the error still exists after re-plugging the two connectors multiple times, please take photos of the plug of the 10-pin connector and the hotend fan, upload log files, and contact the customer support team.
If your X1 series printer has a V9 TH board, please replug both ends of this FPC. (Because the BTB socket is small, the installation of the FPC is a bit tricky. It is recommended that you only plug and unplug one end at a time and do not press too hard.)
Please refer to the wiki for X1 series V9 TH board:
If your printer model is P1P, please replug both ends of this FPC.
Please refer to the wiki for TH board of P1P printer:
PCBs on the toolhead of P1P | Bambu Lab Wiki
¶ Error message
HMS_0300-0300-0002-0002: The speed of hotend fan is slow.
HMS_0500-0400-0002-0020: The speed of hotend fan is slow.
¶ End Notes
We hope the detailed guide provided has been helpful and informative.
To ensure a safe and effective execution, if you have any concerns or questions about the process described in this article, we recommend submitting a Technical ticket regarding your issue. Please include a picture or video illustrating the problem, as well as any additional information related to your inquiry.