Extruder heating up but never stops till error

I turn on the heater say to 150 and it just glows red till i get an error and it gets shut down..
i assume the thermistor is reading the temp the output in repetier shows the temp going to 400 to over 500 like 300/150 bottom bar of window

if it is reading the temp what would cause the temp  not to stop raising

same results with marlin

thanks gary


  • Does it already start raising before you turn on heater? 

    If yes then there might be hardware defect setting the output to high all the time, e.g. a solder bridge from 5v to pin.

    As you read the temperature there should nothing to prevent control only wrong heater pin (then it should not start at all) or the hardware defect or you have a inverting output, but I only know one board having had this for a short while as it is a safety feature to need to turn it on explicitly.

  • is the a way to tell if the heater cartridge is 24 or 12v i have a feeling i may have a 12v cartridge with a 24v power supply...
    bought it quite a while back and don't remember.

    thanks gary

  • 24V on 12V heater is a hell of a power and will overshoot if not limited to 25% power.
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