Brake Controller Trigger Wire?

[jrmgren]

I have a quartermaster. I'm also installing a REDARC tow pro elite. It appears the back seats need to come out to get to the TRM. I tested my control wire under the seat.....nothing. Irritating! BTW, I dont understand the nature of the signal. If the signal is just 0 or 12 volts, what information determines how much brake is applied?

That's the job of the TowPro. It has an accelerometer in it;. When the brakes are applied, it determines the vehicle's deceleration, and applies a variable voltage accordingly.