I've been happily printing on my CR-10 for a couple of months but now there is an issue. As soon as I turn it on the hot-end begins heating. I have replaced the heater and the thermistor but the problem remains. The panel on the control box shows 0 for the commanded temperature, but the actual temp just keeps rising. Anyone know what could be wrong?


1 Answer 1


If you power the printer and it starts heating up the hotend, it most probably is caused by a faulty controller board. More specific, the MOSFET (as in an electronic switch component) controlling the current to the heater element is causing this. MOSFET devices usually fail short-circuit implying that when the MOSFET has failed, the current can freely run to the heater element without being controlled by the board.

If you are handy with electronics, you can replace the MOSFET, but it might be better to upgrade to a newer controller board as there may be other damage as well.

  • $\begingroup$ The description is spot-on and therefore I'm inclined to believe the diagnosis. I'm OK at basic electronics but I'd rather avoid soldering/desoldering MOSFET chips - I'm assuming it won't be socketed? This might be a chance to get rid of the controller box - I find it clumsy. $\endgroup$
    – Bikerman
    Sep 23, 2020 at 12:49
  • $\begingroup$ PS -many thanks. $\endgroup$
    – Bikerman
    Sep 23, 2020 at 13:02
  • $\begingroup$ @Bikerman Usually it is SMD electronics parts which are pretty small, it would require a fine soldering iron, a magnifier and a lot of patience! You already thanked me by accepting the answer! At SE sites we thank by voting and accepting answers. But, you're welcome! $\endgroup$
    – 0scar
    Sep 23, 2020 at 13:05
  • $\begingroup$ As an older Brit I was brought up to mind my manners, so it grates on me when I forget - electronic versions are well and good, but this world needs a bit more civility methinks, so I'll continue my old-fashioned version :-) $\endgroup$
    – Bikerman
    Sep 23, 2020 at 13:22

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