Last week, I lost the ability to zero my z axis through the touch plate, and it puzzled me for several days. The touch plate is connected to the controller at a connection that is designed for a touch probe. When the connection is grounded, a script stops the router bit and sets z to zero.
I checked the wiring and everything looked good there. Then I began to suspect a problem with my Gecko controller, which would have been very expensive to correct. But I ran a wire from the probe connection to ground and everything worked as it should.
Then it finally struck me…I had replaced my 110v Makita router (three prong plug) with a 110v Porter Cable router (two prong plug). I ran a separate wire from the grounding lug on the receptacle to the router, and finally it all worked as it should.
If this seems long-winded, I apologize, but it took me two days to figure this out. My hope is that this will save someone else some troubleshooting time. Moral of the story: the USA neutral wire does not equal a ground; and so, two-prong plugs are not equal to three- prong plugs.