there is a sensor on the spindle houseing that lights up when the tool is in the spindle correctly u can see the light from it from the opertor door its in the area between the #8 and number 10 tool arm you will have to drop the tool arm to replace or to adust it also if u have the style of toolarms that locate on pins look where the pins locate on toolarm it may be packed full of chips so clean them out and the tool arm will reseat right this is what i have to do on the 2 fz12 and fz 15 and the o8s i operate