Hotend temperature too low

Hi, I'm using the RUMBA board and have a temperature problem. Thermistor is type 1. I do not reach the right temp (only 50% of the desired temp). The Host indicates the desired temp. I make an example:

ABS needs 230°C; The host indicates 230°C every things seams to be correct...but at the hotend I have only 115°C :-(.
Thanks for your expectations and your help.
Greetings from Switzerland


  • First if you say host do you mean the target temperature was reached according to firmware response? And manual measurement shows lower temperature? Can happen since measured at oursid eis always lower and if you have in additiona different thermistor then 1  you might get this effect. Also a wrong resistor value (4,7K) which split voltage between thermistor and 5v can cause wrong results.
  • Thanks for your answer. I agree, that the outside temperature ist lower.  May I ask you where I can find the resistor 4,7K and where are the temp tables? Thanks a lot for your help!
  • The 4.7k resistor is on your controller board, normally close to the thermistor pins. Tables are in Extruder.cpp but hard to read. If you select a user defined thermistor in the online configurator, you get a simple editor, where you can set all these values and temp/resistance pairs manually for perfect calibration if you spend enough time.
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