MMU2S Selector not moving

Updated 3 months ago ​by Martin Lexa

If the selector of your MMU2S upgrade is not moving smoothly, or if it cannot reach certain position, the cause is usually one of the following issues:

The selector blade is loose

The blade that is supposed to cut the filament strings was not attached properly or tightened enough during the assembly. It may have moved out of its socket and now it is blocking the movement of the selector.

  1. Release the three screws holding the selector motor in place and pull the motor out.
  2. Pull both smooth rods out. (use the Allen key) and remove the selector head.
  3. Place the blade back in place and tighten it properly.
  4. Reassemble the unit back to the original state.

Filament is bent and stuck in the selector

  1. Release the three screws holding the selector motor in place and pull the motor out.
  2. Pull both smooth rods out (use the Allen key) and remove the selector head.
  3. Remove the broken filament string from the selector and reassemble the unit.

The selector motor isn’t working

  1. First, try powering the printer off and moving the selector by hand.
  2. If that didn’t help or if you were unable to move the selector, release the three screws holding the selector motor in place and pull the motor out.
  3. Push the smooth rods out with an Allen key. You can now easily remove the selector.
  4. Clean any stuck filament and try pressing the left and right control buttons. See if the motor’s shaft rotates. If not, the motor may be defective, or it is plugged incorrectly. Remove the MMU board with its cover and double check this step to see if that is the case. Try also to unplug the cables and plug them back in to be sure.


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