Help please!! I think I bricked my Ender 3 Pro

After discovering my stock hot end was leaking like a sieve I decided to upgrade to a Micro-swiss all metal hot end and direct drive. So I jumped in my truck and commenced to driving the 90 mile round trip to Micro-Center.

Two hours into the build after being as careful as possible the instruction video tells you to heat up the hot end to do a final tightening of the screws, all went well until about 150[SUP]0c [/SUP]then all the sudden the alarm went off and the screen was showing the Ender dragon and blinking on and off.

I powered it down tried to check all the connections and restarted it, same result about 2 seconds into power up the alarm goes off and the screen starts blinking. So I proceeded to try and deconstruct the problem and discovered if i loosened the screw that holds the tiny thermister in the hole the alarm went off and the screen came on. I proceeded to check the thermister for any visible signs of damage, I can see none. So i carefully tightened the screw back and it happened again.

Has anyone run into this before? Do i need to update? I have a hard time believing i damaged it as careful as I was but if that is the case…


It certainly sounds as though there is a connection issue with the thermistor. Is it possible that the insulation on 1 of the wires is worn & when you tighten the screw it contacts the metal conductor inside the insulation, creating a short circuit?

That is what i am starting to think as well. I backed the screw up 1/8th turn and ran a bed-level at temp g-code and heated up and stabilized with no problem. I am going to look for a high temp insulation to place between the screw and wire. crossing my fingers…

The temp problems are as said a broken insulation and/or a loose thermistor.

The leaking is usually caused by doing the assembly in cold state. Same goes for the thermistor screw, which also needs to be tightened while the printer is hot or it will get loose while printing.

As hard as it sound everything on the tool head needs to be tightened in hot state or it will rattle loose. It may work for a while, but in the end you will always get leaks, thermal runaways and clogging due to wrong temperatures.

The thermistor wire is usually heat protected at the end and it should be possible to tighten it quite easy. The problem is when it gets loose and you re-tighten it, you likely stress a different section of the wire. So better do it right the first time and try to tinker as less as possible with the thermistor. You can use screw in thermistors, which are more easy to handle as the thermistor itself is the screw and the wire is free all the time.

I added connectors to all parts of my hotends, so I can just swap components without the need to dealing with the entire cable set and the main board. Especially with component which like to break easy like thermistors, this is a time saver.

On my ANet A8 I even removed the entire part cooling fan and the shroud as I don’t need it. If I ever want to print PLA or PETG on there, I simply screw it back on and connect the wire.

How about some plain old teflon tape?

Update - so I am back up and running (temporarily) thanks to @Ender5r suggestion I actually had a roll of high-temp Teflon laying around. I sandwiched the wire and tightened down the screw and good to go. I am calling this a temporary fix as I am somewhat concerned using it as a long term solution.

@Geit I like the Idea of a screw in thermister i looked into it and there is a good variety out there and they are fairly inexpensive. Is there any you recommend or are they all about the same as far as quality?

Thanks to all again,

There shouldn’t be much difference. I personally did not use these as I bought a bunch of the standard ones.

I am an advocate for screw in thermistors even though I have a few dozen of the cheap wire crap. I have nothing but trouble with them.