Anyone use a redarc brake controller?

[coax]

I've recently installed the towpro but its showing an error code yellow/two red. From the manual this is "There is a short circuit somewhere in the brake light circuit. "

I'm a bit at a loss how to track down a short in the brake light circuit given that the brake lights on both the car and the car+trailer work as expected. As I understand it the brake controller will use input on the brake light circuit to know when to apply trailer brakes, and output current on that when the manual override button on the brake controller is pressed (to light up the brake lights).

I've tapped into the brake wire in the back of the car near where the 4 pin brake adapter plugs in (for simplicity while testing). Validated that the wire I tapped into it has current when expected and doesn't when the brakes aren't pressed.

How would I measure unexpected current draw for the brake circuit? I guess possibly there is some very small short but since only happens when brakes are pressed there isn't an unexpected current draw most of the time.

I found a troubleshooting diagram which indicates its a short to ground on the brake signal wire...realistically they say its just the wire that was run...but I imagine that it could also be on the car's green/white tracer wire or the trailer as well I would imagine since all one circuit. The tap/brake signal wire I ran I am pretty confident there are no shorts on there....so that leaves short on trailer or car somewhere.

Anywho...kind of a general question to see if anyone has used one of these controllers before.

 

[coax]

I think I May have narrowed it down to somethign with the trailer...there is 5v across the +12v and the tail lights. And between tail lights and ground (with nothing connected) there is .2 Volts as well. I wish I knew more about wiring but this seems off to me.