Ok, problem solved, had to increase #define DECOUPLING_TEST_MAX_HOLD_VARIANCE 20  to 40 to maintain heat balance on heated bed, also made deflector for end of fan cowling to deflect airstream away fro

Is #define ENDSTOP_Z_BACK_MOVE 2 set high enough to cause all switches to untrigger? That's the only thing I guess could cause homing fail i z length was set correctly. Also set floor safety margin to

#define DECOUPLING_TEST_MAX_HOLD_VARIANCE 20

#define FAN_BOARD_PIN -9  // was -1 (pins.h says Fan is on pin 9)

#define ENDSTOP_X_BACK_MOVE 1

#define ENDSTOP_X_BACK_ON_HOME 4

#define Z_PROBE_START_SCRIPT "M340 P0 S550\nG4 P1000\nM340 P0 S0"

#define MOTHERBOARD 402

#define Z_PROBE_Z_OFFSET 0

That could be tricky, since min endstop is meant to be at z=0. There is a variable #define ENDSTOP_Z_BACK_ON_HOME 0

#define SDCARDDETECT 49

#define ORIG_SDCARDDETECT -1 // Ramps does not use this port

#define AXIS_STEPS_PER_MM ((float)(MICRO_STEPS * STEPS_PER_ROTATION) / PULLEY_CIRCUMFERENCE)

OK solved it - using the online configurator, set the Fan Pin to Digital pin 4. If you want to do it manually, then add the following #define to your Configuration.h:

#define FEATURE_CONTROLLER 1

#define HOMING_ORDER HOME_ORDER_XYZ

#define BEEPER_PIN             18

#define SDPOWER            -1 // -1 default setting

#define BEEPER_PIN             18

Changed #define SDSUPPORT 0 to 1, so how does that relate to pins.h as shown below?