Adam the Auto Zero needs to be checked, this way when you home Mach will zero the Machine Coords.
The way Mach see a home position is it moves to the switch, it gets triggered, Mach reverses and when the switch shuts again Mach stopos and that is home. If Mach stopped and didnt reverse then the home position would be on a triggered switch which is not a good thing
Remember though when you home you will only see the X Y and Z changuing to zero if you look at the Machine Coords, normally you woiuld be looking at the offset coords and if you have persistant set for them they will reflect a position relative to yoiur last set Offset zero position.
Hood