Ultimaker 2 heated bed sensor error: Troubleshooting seems sound, but problem persists.

[photoresistor 0]

Hi all, I have an Ultimaker 2 that's getting the heated bed sensor error. I've gone through the basic troubleshooting (resoldered the terminal connections to the heated build plate, checked the terminal connections, traced them back to the main board, swapped the bed temp sensor with the nozzle temp sensor). The latter troubleshooting indicated a problem with the heated bed/sensor.

When the printer is off, I can read 108-110 ohms across the temperature sensor at room temperature, and its corresponding pins on the terminal block. If I power the printer on, that resistance drops to zero. If I heat the buildplate in the menu, the reported temperature wavers sporadically between 65 to as high as 110 degrees. I had set the target temperature to 75 degrees. The wavering continued until the printer errored out.

Any thoughts/next steps? Thanks in advance!

[Torgeir 79]

Hi photoresistor,

When you said you swapped the bed temp sensor with the nozzle temp sensor, do you mean that you swapped the connectors on the main board?

I'll assume the latter.. Such failure is one of the most problematic to solve in the electronics circuits, this due to expansion/retraction on the PCB (printed circuit board), however, in this case it should be easy..

Most “probably” it is just the soldering at the surface mounted PT100 thermistor, but can also be the thermistor itself or the PCB track involved here.

You need to remove the heat bed and try resoldering the thermistor.

Another method is to use a heath gun, heating the aluminium side of the heat bed and measure the resistanse during heat in order to observe the failure, then resolder the thermistor and do another test.

Heres a picture of the connection at the heat bed and the PT100 termistor.

Good luck.

Thanks.

[zerspaner_gerd 139]

I measure with me 108 ohms at room temperature, therefore, I suspect a wakel contact.

[photoresistor 0]

Hi photoresistor,

When you said you swapped the bed temp sensor with the nozzle temp sensor, do you mean that you swapped the connectors on the main board?

I'll assume the latter..  Such failure is one of the most problematic to solve in the electronics circuits, this due to expansion/retraction on the PCB (printed circuit board), however, in this case it should be easy..

Most “probably” it is just the soldering at the surface mounted PT100 thermistor, but can also be the thermistor itself or the PCB track involved here.

You need to remove the heat bed and try resoldering the thermistor.

Another method is to use a heath gun, heating the aluminium side of the heat bed and measure the resistanse during heat in order to observe the failure, then resolder the thermistor and do another test.

Heres a picture of the connection at the heat bed and the PT100 termistor.

Good luck.

Thanks.

Thanks for the info, Torgier.

I did indeed swap the sensor connectors at the main board (plugged the bed sensor into temp1, nozzle into temp 3).

I was reading 108 ohms both at the Thermistor and at the Thermistor connectors on the terminal block (the two screws). I observed, prior to resoldering my connections, that the resistance would change if I applied any force to the terminal block. That was why I resoldered.

I have yet to trace resistance all the way back to the main board to rule out faulty wiring. Perhaps that should be my next step. I also have a replacement thermistor on the way. I'm unsure if this is the solution since it feels like I am getting consistent results from my existing thermistor, but I figure it doesn't hurt to have spares.

[Torgeir 79]

Just come to thing about something else, since you mentioned an intermittent connection when you applied a little force to the contact. This contact do not have any connection between the upper part (where the tightening screw is) and the lo part. So make sure that the thermistor wires is completely cleaned for insulation material and clamped well to the lo part of the block. If the wires is of the tiny ones, fold it back so you have double size here.

What you see here also confirm that there is a kind of rupture when bended (expansion) or heated. So I'll think your problem is close to this finding.

Thanks

Torgeir.

[MaxPower 4]

Hi everybody,

I also had a heated bed sensor error and I finaly solved my problem. So I wanted to let you know:

First, I did what I found in this forum, this is:

1.) Resolder the 4 pins of the connection block on the bed.

2.) I also loosened the four screws, got the cables out and shortened the two for the sensor. Someone in the forum said that it is not good if you have solder on wires going into screwed connection blocks. Since mine were with solder on I shortened them and put blank cables back in the block.

Doing so, I could print another hour, than the problem occured again. When I touched the cables or slightly bended the PCB (without glassplate on top) I got an error.

3.) I found out that the problem is in the solder-points of the sensor itself. I first resoldered them but got the error again. Final solution for me: I used two short pieces of cables and directly connected the sensor-solderpins to the pins of the connection block. That did the trick. I can touch the cables and bend the PCB, no more errors.

So I hope this helps someone else. Dont buy a new heatbed, it can be fixed easily.

Last thing I would have done is change the wires from heat bed to the microprocessor. I had a similar problem with my Makerbot, some cables were bended too often and the motor lost steps due to missing signals. Luckily I didnt have to do that.

Good luck...

Max Power