Everybody here has you on the right path.
Why the splitter?
I have 12v for the backlights only (oddly only on the spots, and not the driving lamps). There is no voltage at the end of the red wire and before the lights.
are the backlights on a separate power feed?
You need to work forward from the up fitter IMO. Remember, up fitters are powered with key on, so the relay won’t get a trigger signal unless you have both key on and up fitter on. If you have power at the up fitter circuit, move forward to the relay and verify power.
- is it a 4 or 5 post relay?
with up fitter power on, relay should switch power to the light or ‘load’ - you should see +12v here. if you don’t see it at the relay, that could be your problem. Verify this is connected correctly.
Battery to a relay to a splitter to the lights. I think that’s the correct terminology. There is a 40amp fuse in-line to the + cable. There is a 60amp fuse that is downstream from that but it doesn’t have a window. It’s a little box. This is the SVP kit with 4 Rigid 360 6” lights on a bar.
Minimum: you will have Batt+ & ground/earth into the relay. you will also have a ‘trigger’ wire ( switched power ) and a “load” - this connects to the lights.
Is the relay not enough amperage for all your lights?
If it worked before and not after, whatever you messed with is the most likely place to look.
Yeah, I’m with you here. That said, don’t overlook anything obvious or it could really complicate your troubleshooting.