Hi,

First can you check $5=0 This means that grounding a limit pin triggers a limit. Then it is fairly simple to wire the switches in parallel. Having said that, I notice on your GRBL board that each limit input has +, GND and -. Also your limit switches look as though they have LEDs on them, so maybe one of the board pins provides power for the LED. This probably only means that LEDs will shine at both ends when limit operates. So my best guess is that Red = +5v, Black = GND and White is the Limit sw which goes to ground when triggered.

Hope this helps. It is a pity that we have a plague on as I am only 15 miles up the Fosse from you.

Cheers,

Rob