I'm not really good with pics, but I have an 85 ute as well and under the IGN section on the fuse box cover one of the fuses is marked ENG CONT on the lid. It should run a 10 amp fuse and mine has got a 10 amp fuse in this spot.

The fuse has a brown wire coming out of it and when I look in the engine bay I see a 6-pin connector with 2 brown and 2 blue wires going to it. The connector plug looks identical to the one for the regulator box but only has 4 live pins in it. It is located next to the horn relay and pretty close to the regulator.

Now the problem is I have nothing plugged in to this Eng Cont connector plug as I am in the middle of a CA conversion and I can't remember where I would have placed the mystery box that plugs in to this connector.....but I have recently seen an engine bay photo of an 85 ute and it did have a small silver box (like a relay switch) located on the drivers side (RH) strut tower.

Maybe the small silver box in the engine bay is causing your problem.

P.S. if anyone has a wiring diagram for the late model utes I would love a copy as there are a couple of differences when compared to the earlier models.