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Hot end won't heat - tried with multiple heads

Well, don't know what is wrong with little BoXZY, but the print head is connected up, and the heater block will not come on. I had a jam and took it all apart to clean out the filament, when I went to heat it to clean out the chamber, the block will not come on, also the temperature sensor stays at -26 degrees centigrade.

I shut it all down, changed out the print head for another print head (Entire cylinder assembly) and as a test just turned on the heater in the interface. Same results, it just reads -26 degrees.

Any idea what is wrong with the unit?

Answer this question I have this problem too

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In short, you are screwed, I think. I know I remembered seeing the -26 before.

JustHelping wrote:

"Preface: First paragraph has more detail than necessary, ignore it if it seems intimidating. It's entirely unnecessary to understand it. I just wanted to provide the information for everyone. We're basically just looking for a broken/shorted wire:


To simplify it, if that explanation is confusing (which it's confusing to me and I understand it):

-26 C = CNC head (disables heater power control)

0-360 C = 3D printer head

989 C = Laser (disables heater power control)"


--- It doesn't end well -- See the rest of the article

Installed heated bed, Extruder no longer working..


Thank ypu Gary, so I may have a popped ultimaker board, . . . Sigh.


Uhm, maybe not the Ultimaker board - aside of the power FETs, a 12V regulator, and the stepper drivers, there are no real active components on the Ultimaker board. The analog input signals are passed straight through to the Arduino. I think the Arduino may be damaged. But hey, it's easier to replace than the Ultimaker!

Here are the schematics. Just FYI.


So I need to order a new Arduino, . . . ok. I guess I will do that now Thanks Gary!


Please consider doing my "chassis ground" mod to reduce the chance of blowing up the new one.


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Have you checked your harnesses to verify no pins have pushed up in the harness or down inside the plug? This would be a likely cause and it may have nothing to do with the Arduino Board.

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Oh! You are right. He should look at the connectors as well as try swapping in the Laser Module to see if it tracks. That is an important step - ruling out all the interconnections from the print head to the Ultimaker board.


Actually, right now I have a expensive door stop. I have done all of the steps outlined, even replaced the arduino with a new one and I got nothing. Printer won't come to life at all.

I think I give up, just gonna get a Prusa kit and put it together, then at least I have the info of how it works.

Such a shame, this has been expensive and totally frustrating. And I'm just burned out.


Ken, I'm saddened to hear this from you. You are my rock. If you're reading -26 and you replaced the arduino (programmed and re-loaded the EEPROM) then your issue is simply wiring or a connector. You should check the continuity on the two wires running from the board all the way to the thermistor (from beginning to end through the harness etc). It will allow you to find the short or broken connection. A simple continuity tester will work, or a hardware store multi-meter is probably the best option. Also try switching the two main harnesses for a quick check (don't run the machine with the limit switches disconnected) and see if you get temperature detection. This will quickly indicate or eliminate the black harness.


I will have to try that next, very frustrated. It has not been a good week for poor little BoXZY.


I've had those weeks; I know that feeling. I promise, there will very soon come a point that's there's nothing you can't identify and fix within a matter of minutes. Sometimes you just have to step away for a bit to let the dust settle. When all else fails and you're frustrated, mount a pen or sharpie to the gantry and play with making your own gcode to draw shapes on paper. You don't need temperature detection for the CNC function. It always reminds me how fun a CNC can be.


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Ken Gross will be eternally grateful.
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