Brake Controller Question

dapperdan wrote:
... On the "blue" brake pin however I'm only reading 3.5 to 4.5 volts. ...

If you are not moving and press the brake pedal that is what you get if nothing is connected. A small voltage is sent through a high resistance in the controller to sense if the trailer is connected. The high resistance in the controller means a very small current so the brakes do no operate but the controller can "see" the magnet wiring in the brakes. It will go higher if you are actually moving and hit the brake pedal to stop (inertia). Operating the manual lever will vary the voltage too.

Usually problems like that are where the brake wire passes through the wheel and the insulation cracks causing a momentary short to ground which the controller "sees" as an overload or short circuit.