Before throwing my hands completely in the air I might try swapping Z and X optical switches but not changing pins where they go on C23 BOB, and changing pins in Mach. If the problem moves to X I have one thing, if it stays on Z, I have another. However, I'm not sure I know what to actually DO in either case!! My uneducated guess would be if it moves to X, it has to be the CNC4PC C16 home/limit board, if it stays on Z it has to be C23 BOB or SS..........or Mach somehow.

So....finally got 'round to swapping physical opto switches, Z for X, X for Z. Switched Ports & Pins to match. The problem went to X. It won't back off the switch on X now and it DOES back off Z just fine. In my mind, this makes the CNC4PC C16 the culprit. I consulted Arturo again and he's looking into it a bit before sending me another board/switches to try.

I could still be the switch. I would have physically moved the switches and rewired them so that switch 'X' was now in switch 'Z' position and wired to where switch 'Z' was on the BOB. That would tell you if it was the switch or the BOB. Right now you just know that it is either the switch or BOB.

Precisely what I DID.

Sorry for being unclear, but this is a CNC4PC C16 where the switches are hardwired to a board that in turn hooks to the bob. I've tested every other combo of this as mentioned further up the thread, and what I finally DID was physically move the switches, left the wiring the same from the C16 board to the bob, and told Mach3 it was opposite pins, X for Z. The problem moved to the X. So the only thing left for it to be, in my mind and Auturo's, is the C16 setup. It can be a switch, or the little board they all mount to that also contains other stuff, but it needs to be replaced as a unit. At least it does short of desoldering and stuff. As long as Arturo is willing to send me a new one, I'll do that.

But each switch is still wired to where it was on the C16 board, right? You moved the switches but left the wiring the same so you had to logiacally swap them in Mach.

But each switch is still wired to where it was on the C16 board, right? You moved the switches but left the wiring the same so you had to logiacally swap them in Mach.

Sorry again, as stated above, I did switch the Bob input pins previously with no change. And as far as the C16 goes (the C16 is NOT a bob, I have a C23 bob), those are hard wired so YES they're still wired to the same place on the C16, it's a unit. http://www.cnc4pc.com/Store/osc/product_info.php?cPath=29&products_id=183

A final note on my problem with the CNC4PC C16 and not backing off Z when homing for anyone finding this thread in a future search. Arturo of CNC4PC sent me a new C16 and the problem disappeared, so that was it. All axes backing off just fine now.

Awaiting Arturo's testing of my returned C16 to see if he can figure out how this happened.