Very suddenly i have huge problems with my PID values. For no apparent reason the board shows completely different values than the ones i entered in Marlin. Nozzel temp overshoots well over 250°, instead of the set 240°. Neither reflashing nor changes via Repetier Host or the LCD Panel have any effect. The board is a RUMBA, the firmware Marlin V1 RC2 from Jan. 10th.
The problem occured very suddenly between jobs.
Any ideas?
Try measuring your heating resistor’s resistance. Sounds like it’s about to go bad, with a couple of turns of the resistive wire already touching.
Thanks for the hint. However, im using a heatercartige. The problem realy is the wrong set of pid values i can’t change
I’m with @Thomas_Sanladerer – if it just changed suddenly, look at mechanical failures, most notably resistor/thermistor death from overheating and solder joints. If you’re getting the wrong feedback, changing the PID coefficients isn’t going to fix the problem, just mask it for a short time until it gets worse.
I would have agreed with that if it weren’t that i just can’t change the pid values to the correct settings. Regardless if the heater is defective or not, that should be possible.
I agree. I’m just not sure that’s the problem causing the overheat. I haven’t used a RUMBA, but I’ll ask some friends about it.
I’ve got no problem changing the PID values on my friends RUMBA board - was just doing PID tuning a couple nights ago.
I used M301 + M500 to store eeprom. Maybe you’re reflashing, reflashing, reflashing, but it’s still pulling eeprom values? M502 will reset to “factory defaults (what’s flashed)”, maybe try that?
Thanks guys, i tried a new Marlin version i got from one of the RUMBA developers and it did not resolve the issue. I’ll be able to check with a new heater later today. At this point i have the feeling that i actualy have two problems. 1. broken heater 2. The PID values shown on the LCD are simply not the ones used.
After changing the heater and thermistor it works again. I still can’t see the correct PID values on the LCD, but that seems to be a different problem. Thanks to anyone who helped, this was driving me crazy 
The RUMBA doesn’t seem to update/clear the eeprom when flashing an updated firmware. If you have the eeprom turned on in Marlin then you can only make changes to the values that are stored in the eeprom via the UI, don’t forget to save the changes M500 before powering down the printer or you will lose them.
It does not seem to be a RUMBA specific problem, but a problem of the Arduino Mega bootloader that does not support EEPROM erase. Installing a different FW version overwrote the incorrect settings.
Which version did you use to fix the issue
A very current Marlin provided by a friend who is participating in Marlin development a bit.
do you have a git url for the version your using, i’d like to get the issue fixed on mine
Unfortunately i haven’t. From the file date it seems to have been taken from git on March 1.