crazy Temp numbers...

I was reading an old thread from July 2015 regarding the extruder going into dry run mode.
I noticed a mention of fluxuation of thermistor readings.

This is something I see from time to time and I wonder if maybe it is a firmware issue.

Basically my hot end and sometimes by bed start having temp changes that are just not possible.

On occasion it will cause my print to never even start as the temps are never stable for the 5 or 10 seconds
I have set as a requirement.  I have replaced thermistors several times thinking that was the cause, but the
problem recurs.  Power supply seems stable, and I see no other glitching in the controls.

The thing is that powering down and back up fixes the problem sometimes for days (yes my printer is on almost 24/7 but
isn't printing all that time) Then all of a sudden minutes or hours or days later, I start getting def errors
or I can't start a print and I look and the temp is bouncing around maybe 1-5 degrees at each update.

A quick power down and back up and things go back to being stable.

Is this a known issue? I use FW 9.2.9 currently, but this issue dates back at least 6 months to at least 9.2.8 if not before.


  • Only the fact that firmware averages read temperatures make it only swing a few degrees. Would be much more without averaging effect. What happens is that the analog input reads different values from a sensor defect/cross talk with motors/cable defect that sometime shows up or other electronic problems. I even have seen thermistors that started to jump after 100h of use as they were stressed too much and a defect grow up from screw holding them.
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