I am trying to fix my Ender 3 printer at work. Someone else had it before me and added a direct drive extruder, auto bed leveling, and changed the firmware. He claimed it worked fine, however when I started a print the nozzle was clogged beyond belief so it would not print.
I changed nozzles and had to clean up the heating block a little bit. Once I reassembled the printer and booted it up it shows the error message of Thermal Runaway for extruder 1 and tells me to reset it. I tried powering it off and back on to "reset" it but that did nothing. Within about 10 seconds of turning the printer on the error message shows up and it starts beeping obnoxiously.
Is this caused by something wrong with the thermistor? Everything I have read so far says to check for a faulty thermistor and see if the room temperature reading is 0 °C. However, I cannot do that because it gives the error instantly and will not leave that screen.