Calibrating problem

Hi guys, this is my first post and I'm kind of a noob, so please be kind
So I just managed to assemble my new Prusa i3 kit (bought off ebay) and I got to the calibrating part. I selected auto home from the lcd controller. X axis homes fine, Y axis homes fine, but when Z axis comes close to the end stopper I get a problem. One stepper motor (the left one (next to control board and X motor) stops short of reaching the end stopper, while the motor on the right keeps on going. Now, as the end stopper is on the left side, it doesn't click, so the stepper motor on the right keeps going.. The left one stops at around 8-10mm off the target. It goes up and then comes down again, but only to stop short again.
Any ideas ?
Thank you.

Sounds like Z axis steppers are miswired especially if fed by one driver they use a series connection not a parallel double check their wiring

I think the Z stepper wiring depends on the board. I know with RAMPS there are 2 connectors in parallel driven off the same driver plug-in board.
Can you move the stepper down all the way physically with no power applied?
Using the host software can you manually step the Z axis down until the problem area is reached and check for physical alignment issues?
It's possible to have a binding problem on one side.

Checked and triple checked wiring and connections. Finally I think there was a slight physical misalignment, which I managed to fix somehow.. no idea how . Thanks for the advice guys!