Extruder stepper not stepping

Vertex 3D Printer Vertex - Wiring and electronics
1

Hi,

I have been using my k8400 for about a half year now, but sinds today i have a problem with the extruder stepper, during a print he suddenly stopped.
I have switched the extruder stepper with the y stepper and there he works fine, so its not a broken stepper.
Also i have swapped the stepper driver chips, still every stepper works except the extruder stepper.

Then i checked the main board for faulty components, couldn’t find one. even the 0.9 volts are active on all 4 stepper chips.
The only thing i can find is that when i move the x,y or z stepper there burns a little red light on the main board except at the extruder chip.

Does somebody have any tips on how to fix this?

2

Is the correct extruder selected in Repetier?

3

Yes it is, I use old programs witch used before only now the extruded stepper doesn’t work

4

THe temperature has to be at extruding temperature before the motor will start moving (safety reasons) is this the case?

5

No it’s not.

If I start a program, it will just heat end start to print but the extruded stepper isn’t working and I checked it if there was a current on the stepper but it isn’t. And the motor is not broken beacaus I can switch it and then he works fine