The Marlin firmware provided through Google Drive from Folgertech has thermal runaway protection commented. To enable it, you should uncomment it. Here is what the code looks like by default:// If you want to enable this feature for all your extruder heaters, // uncomment the 2 defines below: // Parameters for all extruder heaters //#define THERMAL_RUNAWAY_PROTECTION_PERIOD 40 //in seconds //#define THERMAL_RUNAWAY_PROTECTION_HYSTERESIS 4 // in degree Celsius // If you want to enable this feature for your bed heater, // uncomment the 2 defines below: // Parameters for the bed heater //#define THERMAL_RUNAWAY_PROTECTION_BED_PERIOD 20 //in seconds //#define THERMAL_RUNAWAY_PROTECTION_BED_HYSTERESIS 2 // in degree Celsius It should look like this (note that the numbers are variable, the correct figures may change depending on your printer):// If you want to enable this feature for all your extruder heaters, // uncomment the 2 defines below: // Parameters for all extruder heaters #define THERMAL_RUNAWAY_PROTECTION_PERIOD 40 //in seconds #define THERMAL_RUNAWAY_PROTECTION_HYSTERESIS 4 // in degree Celsius // If you want to enable this feature for your bed heater, // uncomment the 2 defines below: // Parameters for the bed heater #define THERMAL_RUNAWAY_PROTECTION_BED_PERIOD 20 //in seconds #define THERMAL_RUNAWAY_PROTECTION_BED_HYSTERESIS 2 // in degree Celsius If you experience thermal runaway protection triggering when nothing has happened, you could try various things such as: A) Altering the numbers in the code (_PERIOD defines how long it will wait for your printer to get back to temperature, _HYSTERESIS defines within how many degrees the it will accept before beginning to count down from the number in _PERIOD); B) Performing a PID tune; C) Modifying your part cooling fan configuration as they may be blowing too much on to you nozzle. https://ift.tt/2Hg46m8