Geeetech

My hotend heats up when I turn on the machine, it heats non stop to over 250C. By that time I have to unplug the extruder carriage plug to stop it from over heating.

I tried to upgrade firmware to 37.58 but did not solve the issue, please help, I can't print or use the printer in any way.

And hotend is really hot, or it is cold?

If it is hot, then probably power mosfet is buried. If it is cold, then circiuty about thermistor is bad. If thermistor have capacitor for filtering, then capacitor is bad. If not, then thermistor is bad.

Hot end of medium-sized modern cement kiln, showing tyres, rollers and drive gear. Cement kilns are used for the pyroprocessing stage of manufacture of Portland and other types ... The hot clinker next falls into a cooler which recovers most of its heat, and cools the clinker to around 100 ... The pellets then drop into the kiln.
https://myhr.onl/

You have done best job by writing about Hotend heating up non stop by itself. Great. Thanks a lot.
Caroline,
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It heated on its own, no command to from manual, then tried to tell it to heat up and it continued heating, so the controls aren't backwards.

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