I am having an issue with my extruder not heating, or holding heat after I preheat the printer. I use Simplify 3D, have a FFCP and I can’t for the life of me think of what I could have inadvertently changed as far as settings go. I am new to 3D printing, so it is not obvious to me what could have happened.

Very common problem is to develop a intermittent connection in the wires leading to the carriage due to the constant flexing, so the wire for your heater core might be breaking such that in some positions it isn’t getting full current.

Double check to make sure that your heating settings in simplify 3d has the right tool number. The left one should be tool 0 and the roght should be tool 1.

I had this exact issue with simplify 3d! It happens after you use the dual-extruder wizard for some reason. All you have to do is make sure that the correct extruder is selected on each tab of the settings. Up top select either left or right extruder, then on the first tab make sure you select the main extruder, on the support tab select the same extruder, and on the infill tab also select that extruder. The last thing to make sure is that you have the temperature set correctly on the temperature tab.

I kept having the issue that the right extruder would preheat but once it started printing it tried to print on the left extruder, which had no filament in it. Took me a solid hour to figure out why it was heating but not printing. Selecting the right extruder on each tab is key!

Thanks for replying. It heats fine during preheat, just not when I go to print.

Could easily be a misconfiguration of your start gcode so that it’s switching to the wrong nozzle.

But also working during preheat doesn’t mean you’re not having an intermittent connection. It is very often the first symptom that you lose the connection only when the carriage is moving.

If you look at your gcode for ending you will see the m104 line. You can look for those same lines in the startup for the gcode. Make sure the proper tool numbers are associated with the proper extruders. Then check in your temperature settings the the T# for the tool is correct as well. I had the exact same problem. Now I am trying to figure out gcode for the heated bed.