All the "black" posts on the Z-4000 are tied together. The black post of course goes to the outer-rail. If you run the Z-4000 14V AC accessory output thru the bridge-rectified 12V regulator module, the "-" output of that module is NOT in common with the "black" common Z-4000 posts. The relay module is powered by the 12V DC and, if configured for "low-level" triggering, wants to see the "-" voltage to trigger it. But the isolated-rail is NOT "-" when a wheel-axle connects it to the outer-rail!
The following thread is kind of difficult to follow but explains what's going on.
https://ogrforum.ogaugerr.com/t...12#39441155848604212
So as configured in your picture, it won't (can't) work. If you're sick-and-tired of this and just want a get-out-of-jail card that's one thing - use an isolated power source so let you tie the "-" of the 12V DC supply to the outer-rail. I'd have to think about it but you might be able to use some external discrete components (diodes, capacitor, etc.) to "hack" a trigger to the relay module as-is using the "black" post outer-rail signal rather than the "-" of the 12V signal.
