E1 thermal Runway, printer halted, Please reset, On my Ender 3 pro

I am puzzled (which doesn’t take much) I now have a version 1.1.9.? of the operating system from TH3D site I can preset my nozzle and bed to 215 C and 60 C respectively and I get no error message after leaving it run a half an hour. I tried to print CHEP’s xyz cube again and got this message at the second layer. I then put on the bed level print and…no error message. The print completed as usual.

If anyone has any idea what is happening I would be forever grateful.

Did you re-slice CHEP’s XYZ cube before trying to print it?

Good idea. I shall try that.

I decided to do a vase instead so I sliced an old vase file and it has been printing for 32 minutes now so I guess my problem was fixed. I wonder why a slightly different g code would do that.

Now I will have to test and see if It can understand Prusa’s M600 command so I can do multicolour or material prints without using another slicer. I’m too old and brain-dead to learn all these programs. I have to follow the easy path.

If this does happen again, it sounds mechanical to me.
Why would it idle at temperature just fine, then go wild when printing? I don’t think it’s the gcode, I think its the connection between the thermocouple and the board.
Try this:
Raise the hot end up and release the stepper motors so everything moves freely
Heat the hot end and bed to temperature and monitor for a while
Manually move the hot end back and forth. Watch the cabling, try to give it a workout
Do the same with the bed (assuming your bed moves back and forth
If that does nothing, try pinching the cable from hat end to board and wiggle it as much as seems reasonable. Try pinching near the hot end, near the printer, and in the middle
Do the same for the bed cables

Does anything unusual happen?
It could also be the vibrations of printing affecting the connections to the controller board, but that seems less likely and harder to test.

It prints perfectly when I slice new g code so it wasn’t mechanical it is a difference in versions of Marlin. I just had my friend compile and install the version from TH3D. I only have an 8 bit board so I can’t download any of the 1.2x versions.

Why a different version of Marlin would give a false heating error I have no idea. All is well that ends well. I think my Ender 3 pro is printing better than ever with the new fan.

To add to what @vankichline said, I have 3 rules, well-known to my wife and kids at this point, for electrical/electronic troubleshooting: connections, connections, connections.

When I do electroplating I am constantly having to clean connections.