There are 6 possibilities
1) the thermistor or shorted
2) the thermistor cable is shorted
3) the analog port on the mega is dead.
4) the firmware is looking at the wrong port
5) you have plugged the thermistor into the wrong place
6) faulty ramps board
has it ever worked?
you say you measured the thermistor and it reads 100k. Was that threw the cables? Ie unplug from the ramps and measure threw the cables and the thermistor?
Where did you plug the thermistor into? It should be plugged into T0
what did you set as the motherboard in firmware? Should be "#define MOTHERBOARD BOARD_RAMPS_13_EFB"
have you edited any pins.h files?
If you remove the ramps and the thermistor cable and measure across the two T0 pins, is there a short?
Edited 3 time(s). Last edit at 10/26/2018 07:35PM by Dust.