Encountered a strange fault/error running PID auto tune in Marlin. Even the base command M303 with no extra parameters returns "Autotune failed. Temperature to high ! " @Thomas_Sanladerer or any other Marlin pros have a clue where I should start looking ?
Manually set your temp to 100C first, let it stabilize. Then run it.
Or turn the heater pwm max down from 255. I had to do this on my 800W heated bed because it would overshoot on pid tuning.
I had the same problem because of heaters that were too powerful. I fixed it by creating separate variables (which are now in mainline Marlin) for maximum PID and bang-bang modes. You can use the full heater power outside of PID_FUCTIONAL_RANGE (which you may need to increase) to heat up quickly, but it will reduce heater power once the PID kicks in to avoid overshooting and stabilize more easily.
I’ve also seen this problem when the thermistor wasn’t thermally coupled to the heater block well enough. This caused a delay in the temperature readings that made it impossible to avoid overshooting.
Thank you all ! I was setting up for my flex 3d extruder and thought while updating the firware run autotune for the E3D V5.5 again. Worked before so I was puzzled why not this time. I’ll start with the first suggestion and report later.
Uploaded new e-steps and tried M303 S250 and it worked once … Couldn’t repeat. Got the other stuff sorted and will pursue this again tomorrow. zzzzz