I have a CR-10max that is about 3 years old and can no longer print due to hot end faults. The hot end starts ramping up temperature but is unable to get past 150 °C, unless I turn off the hotend fan then it gets to 250 °C SP, but it is still very slow.
The printer has two PSUs, one that serves the heated bed and the other that serves the mainboard, steppers, and hotend. The hotend PSU is rated for 3.2 A and outputs 24 V. When the hotend is trying to heat it still maintains 24 V, and I have even disconnected this power supply and connected a variable power supply set to 24 V and noted the problem still existed and printer was only pulling 1.5 A while printing. So, the PSU is not the problem.
I did not do any heater tuning prior to these failures. But I did change the tuning parameters to be very aggressive and no change in behavior.
I am beginning to suspect there is a compromised relay or the wiring harness from the mainboard to the point where the heater cartridge is plugged in is compromised. Not sure what to try at this point...