What is it?

A thermocouple is the device that tells the machine how hot the nozzle is. These can sometimes break if they got too hot or are bumped.

The thermocoupler on the flashforges is blue in colour. 

There are two varieties (depending on the model)

to see each go here :

Flashforge Dream (short cable with metal connectors - pictured right)

Finder (short cable with a molex connector)

Flashforge Creator Pro (a long cable fitted differently - link includes so you can see difference)

Flashforge Print Head

How do I know if it is broken

Usually the first sign that your thermocouple is broken is that your printer will come up with the warning asking you to check your wiring. Another sign would be if temperature being shown when running a preheat is very high or low e.g. 1024C. or -20

It is rare for a Flashforge short thermocoupler to break, unlike other brands, as its short length to a connection board on the extruder means it is rarely exposed to damaging movement. However if you have a serious print fail that rises up into the extruder you may accidentally damage the thermocoupler pulling filament off the hot end.


Thermocouples contain very fine wires and should be considered fragile so always handle with care.

How to change

  1. Turn machine off and unplug from power.

  2. Make sure printer is completely cool before going any further.

  3. Remove the plastic cover/lid on the top of the print head to expose the circuit board.

  4. Unscrew the appropriate thermocouple using a flat head screwdriver. Unwind these screws fully and pull the leads out you may wish to use fine nosed pliers for this.

  5. If you have a small shifter you can now;

    1. Unscrew the thermocouple from the heating block.

    2. Pull the thermocouple though from the bottom and discard.

  6. If you cannot access the underside of the hotend while it is still attached to the carriage you can;

    1. Simply remove the filament fan from the left of the print head by undoing the three screws.

    2. Undo the two screws under the carriage that hold the print head to the carriage.

    3. Unscrew the thermocouple and discard.

  7. Push the new thermocouple down from the top taking care not to bend it, crimp or damage the thermocoupler. If you find this difficult you may wish disassemble the print head to give you more space (Disassembly article coming soon.)

  8. Screw the new thermocouple in taking care not to over tighten or injure the cable.

  9. Fasten the cable into the circuit board.

  10. Screw plastic cover back on.

  11. Turn machine on and see if error message is present

We hope you have found this article helpful

Bilby 3D