I just purchased a E3D v5 Hotend and when I attempt to heat it up to 290c as per the instructions, it gets to 290 but then seems to shut off. I am using the Sprinter firmware and a Sanguinololu board. this has worked fine in the past using a JHead Hotend. I have tried setting the THERMISTORHEATER value to 5 and 6. Any ideas as to what may be the issue? Thanks, John
Your printer's MAX_TEMP is being triggered. Either modify the firmware, or use 280/285C for the tightening.