I just replaced my hotend on my Ender 3 Max Neo and after printing a small print I turned it off for an hour then turned it on to print again and it Beeped loudly about Extruder Temperature Too High but I just turned it on and it was cold. I returned it for another one and the same thing. I have check all the wires. Is there a test or reset I can do?
It sounds like erroneous readings from the thermistor. Check it is plugged in well and it will benefit from a tiny smear of high temperature rated thermal compound. Best route is to change it entirely - they are a dime a dozen from Aliexpress. Less likely is a poor connection of the heater so check it’s plug too.
My money is on the thermistor, especially as you just change the hotend. It’s well worth keeping a box of spares like thermistors, heaters, silicon socks, printhead PCB if it has one (I don’t know your model) and even motherboard and a stepper motor depending on your budget. You get a reasonable box of spares set up for the cost of a spool of thread.
Optician
I have tried 2 different thermirister. I did not try the paste but the error is immediate when turning on the printer. The printer is an Rnder 3 Max Neo
I might be a bit late, but I just had the same issue. New hotend still didn’t sort it. Turns out the screw that’s on the hotend temperature wires was too tight. Loosening it off sorted the issue. Hope it helps someone going through the same pain