I checked the resistor: 99.2 Ohms.
Without the resistor it over temps. I can install the resistor and reset with an M999 code and it appears to work ok. I can “turn on” the extruder (there is no extruder, or even power to the RAMPS board, just the Arduino).
I see in Configuration.h the following…
#define TEMP_SENSOR_0 -1
#define TEMP_SENSOR_1 -1
#define TEMP_SENSOR_2 0
#define TEMP_SENSOR_BED 0
I believe the 0 values mean that the sensor doesn’t exist. The -1 values refer to a thermocouple. i.e.,
//// Temperature sensor settings:
// -2 is thermocouple with MAX6675 (only for sensor 0)
// -1 is thermocouple with AD595
// 0 is not used
// 1 is 100k thermistor - best choice for EPCOS 100k (4.7k pullup)
// 2 is 200k thermistor - ATC Semitec 204GT-2 (4.7k pullup)
I think I read that you can just disable the sensor by putting 0 for all of them and that you like to just use the resistor to keep the option for printing without having to reflash the firmware. I’m going to try a different value - one for a thermistor.