2012 RAM Trailer controller hookup.

I'm in the process of installing a Tekoncha trailor brake controller. During preliminary testing prior hooking up the module I find 12V on break switch wire. Is this a high impedance voltage and will drop when I hook up the module. If not, where is this wire picking up the brake signal. I cant find it on the brake pedal switch. Thanks for any help.

I'm late responding to my own post. Further testing reveled the following. I finally found my third brake lite was also on the low side of the brake switch but it was bad. An open circuit
reading with a high impedance meter read the hot side of the brake switch. Replace the third brake lite bulb and problem solved.