[Solved] Thermal Run Away
I was printing a model on my MK3S+ and smelled filament burring look over and saw the filament just running out of the nozzle, so I turn off the power and pulled out the filament (PETG). So I waited until everything cool off. Turn on the printer to test it. I started at 100 then moved up 50c after each stable mark was hit. When I got to 170c +, the LCD only bounced back and forth 168 to 170c. So I decided to replace the hotend and install new Hotend heater cartridge and thermistor which bought from Prusa Eshop. But I still have the same issue. But now I get a hotend error, any suggestion how to fix the issue or where to look. Thanks
I install new Hotend heater cartridge and thermistor and checked all connection twice already, and will new thermistor gave the same issue as old ones? what should I find whit the continuity check?
A failed heater driver is a place I'd look. Check the LED's on the Einsy board. Normally, you will see two green LEDs, but the yellow leds will normally be off unless heating the bed or nozzle.
A jump in the temp display of 2c is nothing I'd worry about. An instant jump of 10c is a problem.
Redo the 50c step test. Watch the Einsy yellow leds. Once at temp, they should cycle on and off. If at say 200c they turn on and stay on, and the nozzle temp keeps climbing - you've proven the driver is probably faulty.
After install new Hotend heater cartridge and thermistor I tested as you suggested the nozzle LED works ok entail it hits 167c. LED starts go off to 169c, then it starts blinking trying to drive the heat over 169c then I get hotend error and printer stop heating.
Could this also mean have a bad driver?
Do I Need new Einsy board?
It's a chicken or the egg problem. The thermistor could be failing at ~170c; the driver; or the controller. Monitoring the drive voltage on the heater element (and the LED) - if the voltage stops, the driver is suspect; if the voltage is still there, it points to the heater (measure drive current to verify the heater is going open - LED on, but no current); or it could be the thermistor failing and telling the Einsy the system isn't heating so the Einsy locks things down. I think the common thermistor fail is a drastic jump in temp: 170 to 0 or 170 to 140 and back to 170.
After talking to Tech support they had me check the continuity of wires, measuring resistance values of heaters and thermistors. https://help.prusa3d.com/en/article/multimeter-usage_2117 , fuses and PSU which were all were good then had me reload firmware, but did not solve the problem. The last thing was to replace Einsy board, which fix all the issue 😊 😊 😊 😊.