Welcome to the SeeMeCNC Community

I've starting printing in PETG and wanted to give it a shot at 245. The hotend heats up quickly as usual and will hold there, but once it starts to print it will start to drop off until it goes to DEF on the display. However if I set the temp at 240 it will sit around 239-241 no problem.

I've tried to do a Auto PID run at 250 but I'm not sure if its actually saving it since I get an ERROR: Wrong checksum when it completes followed by a resend OK.

Is this issue just because I dont have the hiTemp internals?"

Do you have a barrel fan blocker installed? If not, you can print one (http://repables.com/r/828/) or buy one (https://www.seemecnc.com/products/barrel-fan-blocker) and you've got good odds that it'll solve your problem.

Also, what gcode are you sending to do your PID tune?

I do have it installed. It's very odd and seems software related somehow. If I set it to even 241 instead of 240 it ill simply start dropping until too low to print.

I did the autopid calibration using the following line: M303 P0 S250 X0

Hi, it could also be a wiring issue or a psu gone rogue.

Grab a multimeter and check the voltage.
Measure hotend and bed before and after you start the print.


Best of luck
Martin

I think it's unlikely to be a wiring issue, if I set it at 240 it will maintain it at 239-241. If I set it even a degree higher to 241 it heats up fine to it but almost acts as if the max voltage has been reduced and over the course of about 2 mins will drop down low enough to go into protect and stop extruding.

I can manually dial it up to even 250 and tell it to extrude 100mm and it will do it fine and keep it within the proper heat range. During a print however something odd is happening that is causing it.

I've even now just tried to set it at 240 then let the print start and dial it up to 245 after the print is going and it works fine and holds it there, just not if I have it set there at the start.

When the firmware detects a broken signal from one of the thermisters it will display DEF. It has nothing to do with the heat settings. It is a bad thermistor or a break in the wiring, if only for a second.

If there was an issue obtaining the desired temp then DEC (decoupled) would be displayed.

There is also the (somewhat) rare case of the temperature getting outside of the range set for safety, and thus calling itself defective with an accurate measurement.

This sounds like it's having an issue with PID drive max, overmuch fan, or a PID tune. I would attempt to retune the hotend at the temperatures you want for this, as well as looking into the airflow over it, and your fan/initial G-code settings. Or post the first say, 60 lines of Gcode for one of us to trawl through.