Annd, verify if the tractor has 12v live on one wire or not (trailer battery charging) i seem to remember somethung weird about that. When i plugged my trailer in, the trailers 12v battery backfed into the tractor and lit up the running lights! It wasnt as simple as it should have been for reasons i can not remember!
There's a lot of opportunity for "weird" when it comes to the 7 round pin trailer connector. I've come across 3 different and conflicting patterns -- there may be more. The largest pin #1) might be ground or left hand tail/markers. The centre pin might be reverse lights or left hand tail/markers. Etc. It seems to vary by region or country or application. Is a Kubota tractor (or Chinese adapter) wired to conform to Australian RV standards or NA transport truck standards?
By comparison, the 7-pin RV connector (6 flat and one centre round) pattern is pretty much standardized. There's a couple of wire colour variations, but whatever the wire colours if you plug an RV male into an RV female, the trailer lights will function as expected.
If it was me, I'd pitch the round connector and replace it with the RV style rather than mess with adapters. As mentioned above, you don't likely have a brake switch or separate turn signals on a basic tractor but you'll still need the two wires for 4-way flashers on the trailer. And one for the tail lights and of course carry the ground wire, don't rely on the hitch.
You might want the 12v Aux power for something in the trailer (interior lights, powered tongue jack, etc). If you are going to be using this at night, consider the reverse lights -- even if you wire that to a separate manual switch in the tractor. Backing a trailer at night is SOOOOO much easier with reverse lights!
Just my 2¢.
