Hooked up a new Teknosha P3 brake controller, and thought all was well.
Hooked it up to a loaded trailer today with electric brakes, and I get a "NO
TRAILER CONNECTED" message on the display. Manual controller does not send
any juice back to make brakes function. Had set the controller to 6.0 as
per directions. Seems electricity is not reaching wheels, or even past
coupler, which is just long enough if I don't make any turns. Have to
lengthen that a foot anyway.

Guess there is a loose frammel somewhere. 90% of the time, in my
experience, it is a loose or broken ground.

Do I just take a 12 V. battery back there, take the necessary parts off, and
hit it with some juice to see if the brakes are even hooked up? I just got
this trailer, and have not had the hubs off it, and don't even know if it
has brake shoes on it. If I do hit the wire with some juice, the brake
should just function, right?

I am reluctant to do much with the controller, as it says it is easy to
short it out, and it will fry it instantly, no refunds.

Guess the right way is to just jack it up, take the wheels off, take the
hubs off, and see what's there.

Do I adjust brakes like others, with a spoon or long screwdriver until they
just make contact, then back them off until they quit rubbing?

Right?

Shortcuts and diagnosing expertise welcomed.

Steve