Hotend fan not spinning

Updated 2 days ago ​by Tomáš Chvalina

Power down and unplug your USB cable if connected. Open the electronics covering and examine the wiring diagram.

Check the following:

  1. Plugged into the right location
  2. Plugged in with the proper connector orientation
  3. Plugged in completely and making good electric contact

You can easily test the nozzle hotend fan function from the LCD menu Preheat - PLA. When the hotend temperature reaches the 50°C, the fan should immediately spin up.

If the fan doesn't spin up, you can unplug it from the electronics board and test it with the 12V DC power source. If the fan spins up with an external power source, check all the electronics wiring and fuses MK2/MK2S Electronics Wiring in RAMBO board.

When the hotend fan actually should spin

Hotend cooling fan cools down the top part of the hotend (heatsink) from the heat which is transferred from the heater block. It always starts up when hotend temperature reading reaches 50°C and spins for the whole duration of the print! If the fan is not functioning, you can expect the nozzle to jam after the first few layers.

!Always make sure that the fan is pushing the air through and around the heatsink and not out!

Propper orientation of the hotend fan can be checked at the photo down bellow. 

Do not hesitate to contact us at if you would have any following questions.

How did we do?