My mini is wired exactly as shown in the OHAI instructions. Specifically, there are Blue and Black wires going to (2) of the pins on the 6-pin header just above Z-Max.
I cannot find any documentation for that connector. It is silkscreened “X18”. Some comments I read, and thinking about how the Mini leveling works, I have to conclude that those two pins are duplicative (parallel) to the (S) and (-) pins of the Z-Min socket.
It is my understanding that shorting those pins (whether manually, or via the nozzle tip touching the build plate washers) should do exactly the same thing as closing the Z-Min switch. The nozzle-to-plate connection is, effectively, just another Z-Min switch in parallel with the physical Z-Min limit switch. G29 looks for closure of the Z-Min limit pins to record bed contact.
