Bed Thermal Runaway Problem Taz 6


Background: I’ve been using my taz 6 for about 3 years now without any major problems. The only upgrades I’ve done are to the modular print bed and the TAZ AeroStruder Tool Head, besides that everything else is stock.

Problem: 20 minutes into a print I get an error message that reads: “BED TERMAL RUNAWAY, PRINTER HAS HALTED, Please Reset”. Once I get that message and reset the printer, the bed won’t heat up at all.
After, opening everything up and checking wire connections, the printer started working again! only to repeat the same failure 20 minutes into the print, and now I am where I was before, the print bed won’t heat up.

Summary of what I have done so far:

  • I used a multimeter to check continuity on all of the wires leading from the Rambo to the heated bed. I am assuming the larger set of wires is for the actual heating of the plate, and the smaller ones are the bed thermister. Both sets of wires are good for continuity. It could be that the act of me checking everything out some of the wires back in place, and then once I closed it all up something slipped… I am not sure how likely that is.
  • Checked for fuses: I looked at the main 15A fuse and that seems to be in check.
  • I have cleaned and dusted around
  • I checked for loose connections along with the wire leads, everything looks ok.
  • I was not able to really how the wires are connecting to the build plate since these are under a mesh of adhesive padding, I am not sure if there is more to check there.
  • I noticed that there is a solid red light on the RAMBo when I try to heat the plate, and the plate does not heat up, I get a bed heating failure message. The one time it did start working I saw the red lights flash, I am not sure what that means.

Possible problems:
-Bad RAMBo- I might need to replace
-Bad build plate heating element, replace the heating bed
-loose wires somewhere.

Any further help would be greatly appreciated. I am all out of ideas at this point. Thank you in advance for your assistance!

Sounds like you may have already checked this but have you checked the thermistor and heater continuity at all the positions of the bed? (Like back and forth) Maybe after lots of moving back and forth a micro fracture in the wire could have occurred?

I have not done that, but it sounds like a good idea. It’s possible that it’s a wire movement that causes the print to fail. I’ll check that. Thanks!

You could always swap in the old bed if you still have it. I’m paranoid and kept all that stuff.

I should have kept it!!! but since I have been using the new one for over a year, I decided to get rid of the old one.

Update-- I have replaced the bed, and the problem still persists. I think this must be an issue with the heat bed connection from the RAMBo all the way to the heated bed. Any idea of how I can replace these? I see that on the website they are out of stock. Can I just buy the stock cables else where and make them my self? any ideas on how to do this?


It looks like the power supply cables (the top two ones shown in the image) were a bit loose. I made sure these were tightened and re-attached everything. I also used black tape (pictured) to keep the sides of the cables to the casing so that it would decrease the stress on the cables. It seems like these were loose, and not supplying the heated bed with power. The cables were just loose enough that the vibrations of the print would shake these out of place.

I’ve received the following errors: Bed Thermal Runaway, Bed heating failed, and err: Mintemp Bed. I opened up the side and found the wiring to be tight. anyone have other suggestions?