Taz Bed Not Heating Up - Help with troubleshooting

Hi All,

I have had a Taz5 for over a year, no real issues. But the bed has just stopped heating up at all. I am using Cura, I set the nozzle and bed temps as usual, the nozzle heats up as expected the bed doesn’t al all.

I have checked all the connectors, they all seem perfect.

I have shut down and restarted Cura, and also the printer itself with no change.

I undid the bed connector and measured the resistance across it at 2 ohms, so its not open circuit so I assume its ok?

Can anyone help with other things I can check to try and work out whats wrong?



There is a 15 amp automotive fuse on the Rambo board, check that.
The thermistor is located in the rubber bulge under the bed heater. It should still register heat changes. Take a potato and microwave it, then stick it on that sensor with the bed cold but dismounted and see if you get a change in reading. You can also look up the resistance and test that with a meter too. The connector at the control box is a potential failure point.
The bed should have continuity all the way back to the Rambo board on the heat wires, check at that plug for continuity.
If the bed checks out, the fuse is fine and the thermistor is fine, it could be the board, but that’s a rare failure. The control box plug, wire harness and the thermistor are the most common failure points. And the fuse I suppose.

Awesome info mate, thanks very much. I assume the “Rambo” board is the main board in the control box on the side? Will have a look and post what i find in case its useful to someone else later on. Much appreciated!!

Yes, that’s correct. Rambo is the model name of that particular board. You’re welcome!

Wow, pretty surprised by this!! When I removed the connector for the bed, the connector itself was quite charred inside, I then opened the enclosure, and unplugged and remove the loom, and the connector and wires were very obviously heat damaged and consequently weren’t making a connection.

I am an ex radio tradesman so just for now i have fitted individual connectors to each of the wires and ran the loom out of the hole in the enclosure, plugged it ll back in and its working perfectly. So will see if I can order a new male/female connector and fit them.

Not sure whats caused that to be honest!!

Actually thinking more about it, that’s not very good. I think i might contact Lulzbot and see if they can send me a replacement loom and plugs made up under warranty. I am a little surprised a fuse or whatever didn’t blow before this, it might be something they want to look into a little more, could of course just be one off problem.

Full draw of the bed is theoretically 15 amp. That connector isn’t rated for it. https://forum.lulzbot.com/t/adjustable-heat-bed-glass-mount/38/1 details here
A replacement connector option rated for 20 amps is this one

You can also get replacement stock connectors and bed harnesses on itworks3d.com
That issue only affects the taz 4 and 5. The 6 uses a different connector and 3 and below did not have a panel mount disconnect.

You sir are a legend!! Looks like I have a nice little job to do :slight_smile:

Glad I could help!

Its one thing I love about the modern world, and internet forums in particular. We are all so connected now, if a problem occurs like this one with me, it pretty much always seems someone else has found a solution or is able to offer advice on how to fix it. Its great, very much appreciated mate, happy printing :slight_smile:

Thanks for having this post here. I just had one of my three Taz 5’s have this exact problem. New parts coming from ITworks in a couple days, but I’ll have to look into getting those other connectors for if this happens to my fleet again.