Vertex k8400 not heating


Hello everyone
I have a vertex k8400. With 2 extruders.
The first extruder will not heat it goes after 20 minutes at preheat only up to 183 degrees
while printing the temperature drops to 170 degrees.
But the second extruder is working fine.
I have tried everything. I even installed a new heat sensor.
can someone help me please


Did you check the wires from the heating element to make sure they are tight?
Check the plugs on the print head to make sure they are ok as well.


yes everything is ok.