Bed temperature problem: bad thermistor?

[emanuelefavaro]

Hi there,

after assembling and successfuly making some test prints, one of the cables going from the motherboard to the bed thermistor broke, maybe because of some stress during assembly or bad soldering, don't know.

I resoldered it but now the display is stuck on 12°C (see pic), even if the bed is heating up correctly.
Obviously this error doesn't allow me to print anything.

I tried unplugging the thermistor cable from the motherboard, display still says 12°C.
If I short the thermistor cables, I get a MAXTEMP BED error and the temperature goes up to 355°C.

Would this be fixed replacing the thermistor?

Thanks,
EF

[William]

Hi, you mean that the hotbed line is unplugged from the motherboard and the screen still does not show the room temperature of the hotbed? If that's the case, maybe the motherboard is broken.

[emanuelefavaro]

Wonderful.

Any ideas on how I can check to make sure?

Thanks a lot.

[William]

Hi, You can unplug the hot bed line to see the hot bed display of the display to see if the motherboard is normal. If the room temperature is still not displayed, there is a problem with the motherboard. You can also measure the thermistor of the hot bed to determine if the hot bed is normal.

[emanuelefavaro]

Well, I swapped the extruder and the bed thermistors.

The bed thermistor indicates the correct room temp, while the extruder thermistor, attached to the bed port on the board, indicates 11°C which is the same uncorrect reading I get with the bed thermistor on that port.

I suppose I have to file an RMA for the motherboard at this point.

[William]

OK, glad you found the problem.

[Super]

Hi.
I have the same issue.

I have a i3 Pro W that I have not used for a while, but when I went to use it yesterday, I found that the bed temp was showing at 43°C when I turned the printer on.

I successfully started a print, but after half an hour, the bet temp went way up and then the printer shut down with Err: MAXTEMP BED.

I unplugged the printer and allowed it to cool overnight and today when turning the printer on, I received the same error with the bed reporting temp of 168°C.

I have attempted to unplug the the thermistor as well as swapping the bed and print head thermistors, but error does not change.
I have also re-flashed the firmware with the latest but that has not helped either.

Any help would be appreciated.

[William]

Hi, You can try to unplug the hotbed on the motherboard and check the display.

If the temperature still shows high temperature, you need to replace the motherboard.

If the temperature shows zero or negative temperature, replace the hotbed.

[Super]

Hi William thanks for the reply.
as I mentioned earlier, I have tried unplugging the hotbed thermistor as well as swapping the thermistors for the bed and the hotend.

The error does not change.

Looks like my current choices are to replace the motherboard or get a new printer.

[William]

Hi William thanks for the reply.
as I mentioned earlier, I have tried unplugging the hotbed thermistor as well as swapping the thermistors for the bed and the hotend.

The error does not change.

Looks like my current choices are to replace the motherboard or get a new printer.

Hi， If you unplug the hotbed line temperature is still very high,

you need to replace the motherboard.