Ender 3 Pro - Troubleshooting

After a couple of months running two Ender 3 Pros, I’ve invariably run into pretty much all the common issues you can encounter with your printer.

Thermal Runaway Error

So much fun this is. Said no one ever.

Important! This can be a potentially serious issue, so please do your due diligence! The below may not fix your issue. Please stay with your printer when printing with this type of error, this is a fire hazard if not properly resolved.

The modern generation of Ender 3 Pro (post 2021) come with thermal runaway protection, which is a good thing, and shuts down the printer in the event of a wild change in temperature (primarily to prevent the printer from continuously heating the nozzle to unsafe levels that can result in a fire). However, I began to experience regular issues on one of my printers (darth, in case you follow my setup), and checking on OctoPrint, I noticed wildly fluctuating tempreatures during a print that ultimately resulted in a thermal runaway protection error (I didn’t take pictures at the time, will add if it happens again).

This is what I saw:

Wildly fluctuating nozzle temperature that eventually results in a thermal runawaay error and emergency halt. The first time this happened, I was 11 hours into a 12 hour print, and then it would happen constantly a few minutes into a print. Doing a little research, all indications pointed to the thermistor (the sensor on the heating block where the nozzle is) being faulty. So I went to Amazon and ordered replacements. Awesome! 3 weeks to get these to fix my printer… boo!

A couple of days later I thought to myself (I have lots of these kinds of brain farts): let me take the nozzle housing apart and see if maybe there is an obvious issue (something has come loose perhaps). I did that, and then using the small screwdriver that is included with the printer, gently loosened and then tightened the screw holding the thermistor to the heating block. Gentle is key, use only two fingers with minimal torgue, as the thermistor wires are very thin and can easily break if you use too much force.

Apparently this was enough to get it all working again, with a solid and consistent reading from the thermistor… he said, hoping. Turns out the next large print I did I had the same issue again.

So, now we wait for replacement thermistors.

Update Finally got replacement thermistors for the nozzle, and this did fix my issue, and I’m now printing large (multi-day) prints without any fluctuations. For now, no more hard resets and thermal runaways. (Not a trivial fix, but if you have and Ender, this is par for the course).