Printer inverted Y-axis
This blog post shows 3 main solutions:


Flipping the motor cables (As suggested in the other answer)
Switching the x and y-axis:
This may switch the direction of your y-axis depending on the way your printer is setup)
Change the direction of the axis in firmware which you can see below how to do:



  "When the solution opens up, you will see many different files open. You need to navigate to the Configuration.h file. Within this file scroll down to the following lines of code:"


// Invert the stepper direction. Change (or reverse the motor connector) if an axis goes the wrong way. 
define INVERT_X_DIR true 

define INVERT_Y_DIR true 

define INVERT_Z_DIR true



  "This is where you need to switch the values around. If they are currently true, change them to false and if they are false, change them to true. Due to the fact I was having issues with my x-Axis, I have changed the above to the following:"


// Invert the stepper direction. Change (or reverse the motor connector) if an axis goes the wrong way.

define INVERT_X_DIR false

define INVERT_Y_DIR true 

define INVERT_Z_DIR true