So I got kinda lucky... I guess.
Looks like whoever installed the trailer wire harness (7 pin) ran the red, blue, and white wire from the trailer harness to the battery/engine bay already and just bundled it up for that day when someone (me) would install trailer brakes. So I ordered a trailer brake controller (
this one, universal brake controller) and hooked it up according to their directions with the signal wire from the brake pedal (as discussed here), Hooked up the blue wire to the trailer brake controller output and the white wire that was not attached to anything (odd... since the trailer lights were working) to ground on the battery and the red line (which was connected with an inline fuse to the positive terminal) to the rear battery fuse box... Trailer brake controller was connected directly to the battery (with
20amp automatic reset circuit breaker) and ground. All voltages check out in the front:
12+v on red line
ground on white line
12+v on brake signal line to controller
but when I check at the harness for the 12v constant power supply I am getting 6 volts... how is that possible? Also the trailer brake controller is not showing a trailer connected when one is (equipped with brakes), nor is the trailer getting any power to accessories, but the brake/turn/running lights function correctly. Trailer brakes are not functioning either both with trailer attached and voltage test at trailer harness (trailer not hooked up)
Observations: I did note that when I traced the red line from the trailer harness it went to the rear passenger side and came back to the center before making its trip to the engine bay... assuming it was needed to power some control module so power was not drawn directly from the vehicles rear lights because (observation #2) the trailer lights did not work when the fuse for the red line was removed...
Leaving on a trip tomorrow cross country with this trailer and hoping to get the brakes working and the auxiliary power. I feel like its something small I am missing. Would appreciate any incite you guys may have.