Brand new A1 heatbed temperature abnormal error

Bambu Lab A1 Series Troubleshooting
1

“the heatbed temperature is abnormal; the sensor may have an open circuit”

I received a new A1 yesterday afternoon. Set up, run the calibration and run a couple of prints - one that lasted about 5 hours and a couple of small ones. Everything seemingly going well.

This morning I ran a small print which went fine but an hour or so later I go to run another print and I get an error about the heatbed. Since then I have been getting consistent heatbed errors. The bed itself does get hot but it seems like after it reaches a certain temperature or something it goes wrong and raises the error and the temperature readings are no longer correct.

I’ve tried:

  • Factory reset
  • 3 different firmware versions (oldest, somewhere in the middle, and latest)
  • I’ve tried measuring the resistance of the power (47 ohms) and the signal (125 kohms - a bit high compared to the 100 kohms expected but not crazy)
  • I’ve tried reseating all of the cables

I have a ticket open with Bambu but I thought I’d reach out and see if anyone knows anything else I can try in the meantime because I’m sure it will be at least a couple of days before I hear back and I only have the weekends to do 3D printing so trying to see if there’s still a chance I can print a larger object this weekend. I am assuming this is a “wait for Bambu to respond” thing though :stuck_out_tongue:

Thanks all

2

The resistance measurement looks like it is telling you something. A 25% error is pretty big.

I’d bet it’s exactly like the message says - an “open” which may not always be open. Temperature causes expansion and contraction so there is physical movement as the heater heats the build plate besides the actual build plate motion tugging on wiring. I’d trace the heater wires from the build plate to the circuit board they plug into and make sure all connections are tight and the wiring isn’t damaged, pinched, or cut anywhere along its length.

As an aside, the extra 25k ohms you’re seeing could be a weak connection somewhere or a wire cut, etc.

3

Yeah that is a good point.

I think I have done as much tracing as I can do without disassembling the heatbed itself but Bambu doesn’t have any docs on this so I will just have to wait and see what they say!

Thanks for taking the time MZip :slight_smile:

1 Like
4

Good luck! Hope you get it sorted soon.