Hot-end shutting off half way thru prints

Ok, got a weird one and I'm out of ideas on what could be wrong. Trying to run a print that's about 2 hours long and about 60-70% through the print, the hot end cools down, but the printer keeps trying to print, causing the hot end to jam up... And the print to fail. Pull the plug, clear the jam and start again and it starts off fine until the middle of the print then the hot end just shuts down again. Rinse and repeat.

This is with the stock J-head (I'm sitting on my E3D's waiting for Gordon to realse the new design files). I've checked all my connections and everything is solid. Re-sliced my STL to make sure it wasn't bad gCode. Still happening.

Short of a failing ramps board or a bad hot end, I'm out of ideas on this one.

- Chris


New Member
Does the software give you bad temperature readings and have you put a meter on the wiring when it fails? An intermittent short might cause your symptoms. Particularly check the thermistor. Movement or expansion from heat may be triggering a short.


Staff member
Does it fail in the exact same spot each time? It could be the thermistor is shorting our on the hotend or in the connector. I've had this happen but it was usually pretty random... Swapped the thermistor and it was ok.

We're working on releasing the designs... Just tweaking any last parts and of course no time :)
It's not failing in exactly the same spot, but within about a centimeter difference each time. Unfortunately with the length of the print I've never actually caught it happen in the act. I could try doing a preheat and manually ramping up the z axis to see if I can get it to stop at a particular place.

What should a meter on the thermistor read at temperature and when cooled down? Assuming I should measure this both at the extruder and at the RAMPs side to determine if it's just a bad wire.

Gordon, will you be selling upgrade parts ala-carte or only as a package? If this turns out to be a bad j-head or thermistor, I may just want to do an incremental upgrade starting with the extruder module just to get my E3d's printing.


New Member
If it is a 100K thermistor, it should read 100K ohms at room temperature. It would read progressively fewer ohms the hotter it gets. If you read zero, there is a short. If the problem is intermittent, it may be difficult to get a reading on that :(
Well, I feel pretty stupid now. I started undoing the zip ties to get access to the thermistor connector to take a reading and found this. Looks like the wire had pulled out of the pin and was barely making contact. The tension on the cable once the z-axis was up a few inches must have been enough to wiggle it the rest of the way loose and break the connection.