[Chris53]

From the screen (enter next command)type in (D I ) and hit the enter key then (D S) and the enter key. This will display all of the proxswitch functions on the screen . If you rotate the spindle by hand you will see the spindle switch go on then off as it passes the orientation position for the spindle. If it does not change then it is a good bet it is bad.
When you are done checking the switches then type D I enter then X and enter- if you don't then the switch screen will stay up superimposed on top of whatever screen you are in- this can be usefull for troubleshooting but is distracting and when you change out if the D I/ D S screen you loose the labels for the individual switches.