in latest marlin [
github.com]
ie in the file pins_RAMPS_14.h
#define TEMP_0_PIN 13 // ANALOG NUMBERING
#define TEMP_1_PIN 15 // ANALOG NUMBERING
and a bit lower down
#define TEMP_BED_PIN 14 // ANALOG NUMBERING
t0 is pin 13
t1 is pin 14
t2 is pin 15
Just swap these as needed..
ie to swap t1 and t2 change the following
#define TEMP_1_PIN 14 // ANALOG NUMBERING
#define TEMP_BED_PIN 15 // ANALOG NUMBERING