TAZ Heated Bed - No Longer Going Up to Temp

I’ve been happily printing away on my TAZ for the last two weeks or so with no issues at all (other than needing to level the bed & reset the Z-home to get the height just right).

Over the weekend, I noticed that my heated bed can no longer get up to 110C. I’ve been able to get it up to temp in about 13 minutes until two days ago. I just tried it again this evening - going from a powered off 21C to 65C took it over 20 minutes and it seems to have stalled out around that temp based on the temperature reading in Pronterface.

If I put my hand above the glass plate of the bed, it feels like it’s much closer to 110C than 65C, but I don’t have an accurate way to check it. I did print with PLA & ABS though and this definitely feels more than 5C hotter than the 60C setting I was using for the PLA. The wiring to the heater and the thermistor look fine as far as I can tell.

Has anyone else experienced this issue? Any ideas of things to check to troubleshoot?

You really don’t need to run at 110C on the TAZ. We run at 85C and you can probably do lower. 110C is really getting up there, as you’ve saw. The way a lot of other heatbeds are set up (Prusas, AO-100, etc) the actual temp on the glass is lower than 110C when it reads that. On the TAZ, what you are reading on the thermistor is closer to the glass temp. So really, you can do 85C, perhaps even 65C, and still be able to print ABS happily.


Thanks Jeff - I’ll give 65C a go and see how it turns out. The TAZ manual actually said to use 110C for ABS printing (page 47), so I was just going by that guidance.

I’m still concerned that the bed has stopped going higher than that temperature (or at least stopped reporting that it’s higher than 65C) since it definitely did it just fine for a week and half and suddenly stopped. If I do have to go up to 80-85C, is there anything I can check to make sure the bed is safely getting there? I’m a bit worried if I tell it to go to 85C now, it’ll hit the actual temp, but only register 65-ish on the thermistor so the firmware will keep trying applying heat to the bed.

I just ran the octopus print with the bed at 65C and everything stuck to the bed just fine - so thanks for the tip about printing with a lower temp on the TAZ.

I did go back and check my notebook from when I was testing the printer on day one. To get to 65C then, it took 3 minutes and 25 seconds starting at 21C. Tonight, same machine, same power supply, same room, same ambient temp - quite literally nothing changed - it took 16 minutes and 25 seconds to get to the same temp. AC vents were closed & and the AC itself was turned off both times. No idea what is causing the massive increase in heating time, but at least I can keep printing.

I just noticed this problem today too…bed can’t get past 75 deg C

Checking the fuse, as suggested in this post for an extruder that cannot get to temp. https://forum.lulzbot.com/t/hotend-no-longer-heats-up/127/1

We are including an errata in the TAZ manual that says to do the bed at 85C not 110C.

adambryan: With the printer unplugged, pop off the cover to your electronics and see if you see any obvious wiring issues.

Just checked all my wiring…looks good.
I think it is a sensor issue.

I have the machine set to go to 110 deg C. It says it is at 84.5 deg, and has been for the last 20 minutes. But I put in a small thermocouple hooked to a meter and it is reading 114 deg C.

So for some reason it is not sensing correctly and is actually hotter than it thinks…not sure how to fix this? any thoughts.

Also similar with a bunch of exploring as to what is happening on mine…


jebba: I checked the wiring and nothing looked unusual as far as I could tell. I’ve been talking to Claudio via email and have and RMA # ready, so I’ll be UPS’ing the bed back for you guys to see in the next day or so.

In case it helps you or anyone else on the forum, what we found was that my bed’s resistance was higher than it should be. The first day I measured it, it was 1.8 ohm and now it seems to be around 1.2 - 1.4 ohm - I’m not sure why it varies a bit, but it’s never been lower than 1.2 ohm anytime I’ve tested it. It sounds like Lulzbot HQ beds are showing about 0.8 ohm based on info from Claudio.

I have a friend in town that also bought a TAZ so I took my heated bed over there to test. When hooked up to his machine, my bed shows the same issue - very slow to heat up it was just over 35C after about 6 minutes of heating. When we popped his bed on again, it was up to 75C in exactly the same amount of time. His has no trouble getting up to 85C or even up to 110C. I checked his bed resistance and it was 0.8 - 0.9 ohm at room temp.

My bed takes about 45 minutes to get up to 80C and it can’t get to 85C at all. After waiting 15 more minutes after it it 80C, it actually went down a bit in temp even though power was still being applied (the target was set to 85C). I attached a thermocouple to the center of the bed while doing this heating test and in my case, my thermistor is accurately showing the correct temp, but the bed itself can’t seem to heat up past 80C (on the thermistor / 85C on the external thermocouple) no matter what. In case you’re interested, I published the timing test results here:


All that said, I’m going to ship my bed back to Lulzbot HQ so this can get figured out, but it definitely looks like there is an issue in the heater itself.

You may want to check one final thing…

From a cold start, can you specify a temp of 110c, and then while watching the readout from printrun, see it go to 110C (only once, then it will start cooling back down) or at least that’s what the software will tell you.

e.g… Mine will do this exactly one time if already heated… Here is my cold to 110C numbers and curve, but if I try it the next time, when the bed is already warmed, it will never get to 85, and will take forever to get to 75-80…


With that said, you may indeed have a different issue, but the similarities are just too close to home for me :wink:



I really appreciate all the information we’re collecting in this thread. Thanks. :slight_smile:

My Taz 3 has been heating for the last 45 minutes. I set to preheat for ABS (230/85) and I’m at 103/70. This issue started yesterday and my max temp since has been approx 170/76 (extruder/bed). Any suggestions?

Reflashed the firmware using the Marlin.tar.bz2 file from Downloads. Extruder maxing out @ 183 (set @ 230), bed maxing out @ 70 (set @ 85), and selection beep has disappeared. No real improvements other than lack of beeping, seemed worth a try for lack of any other obvious culprits.

There’s a couple things we need to check- the resistances of the hotend/heated bed, and the power output of the power supply.

With the printer turned off and unplugged disconnect the heat bed from the wiring harness and test the bed for the proper resistance. The smaller wires are for the thermistor and should read ~100k at room temperature. The larger connectors are for the heated bed heater coils and should read between ~0.8 Ohm.

Disconnect the hot end from the wiring harness and test hot end for the proper resistance. The smaller orange wires are for the thermistor and should read ~100k at room temperature. The larger red wires are connected to the heater resistor and should read between ~4-7 Ohm.

Send in your results to Support@LulzBot.com and we’ll walk you through the rest of the process. Include your order number/order contact information and we’ll be better equipped to determine what kind of resolution we can offer.



Hello, to add to this thread, we have a TAZ 2.1 and it just started exhibiting this same problem this week–we’ve had it a couple of months. From a cold start, we try and head the bed up to 60C to print PLA. It takes around 15 minutes and it never gets any higher than 49-50C on the display. Previous to this, it would heat all the way up to 110C (though we don’t use that temp any more) in just a couple of minutes.

We have a support ticket open and have ordered a meter from Amazon as we were asked to measure the resistance on the bed and hot end. It’s unfortunate that we have to jump through some hoops to even get the troubleshooting done, but just a heads up that we’ve got a TAZ with this same issue.

Ah, you don’t need to order a multimeter. If support asked you to test it, it is under the presumption that you have such gear. If you don’t, you don’t need to get it. We can issue an RMA for the bed if it has gone out on you. I’ll point them at this thread.



We got the multimeter in and tested the unit. When we sent the readings to support, we were told that our heater coils are running about 80% high. They are sending out a new assembled heatbed today, so we are happy that our issue was resolved so quickly by support.