Hotend & Bed Read 2000C - Even when sensors disconnected?

  • Hello,

    Yesterday I had a print lift off the bed and get stuck to my hotend. I caught it in time to remove the giant blob but while I was doing this the machine experienced some kind of fault and now the Hotend & Bed both read 2000C. I have tried turning the machine on / off with the bed / hotend sensors disconnected and it doesn't make a difference.... web UI still shows 2000C for both.

    Additionally I tried searching how to reset heater faults... I found another thread that suggested M562 P1 and M562 P2

    This clears the "fault" display in the web UI, but when I power off / on again the fault returns.

    Hotend / Bed Error Display

  • Moderator

    @dirtybirdnj Most likely, you've shorted the hot end 12/24V to the 3.3V thermistor. As it says here

    Create a short between a hot end thermistor connection and an extruder heater or fan connection. On many electronics - including RAMPS and Duet 0.6 - this will kill the processor. However, this type of short is surprisingly common in 3D printers, so you're out of luck because we've taken precautions against it. The most damage you are likely to do is to blow the VSSA fuse. Although that fuse can be tricky to replace, it's quite easy to bypass with an external fuse. So if you are trying to destroy your Duet, blowing the VSSA fuse doesn't really count. Oh, and to spoil your fun, in PCB version 1.02 and later we use a self-resetting fuse.

    So it depends on your Duet. What Duet do you have, and what version (says on the PCB)? See this guide for replacing/bypassing the VSSA fuse:
    And there are a number of forum threads like this:


  • 2000C indicates a short on the thermistor connections. -237.x C indicates an open.

    Since you have 2000, you still have a short. Unplug the connectors for those sensors. If you still have 2000, you have a damaged main board.

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