Weak Braking w/ Tekonsha P3

Thanks for the responses. The brakes were properly adjusted during the 2012 season and prior. During that period I was able to lock up the trailer brakes on current and past trailers using the manual lever. Earlier today when I was taking my readings, I did see voltage changes when I changed the boost setting, but based on the power settings having already been set near the highest, I don't believe they can be adjusted upward enough to get to the point of adequate braking. The contacts on both sides of the 7-pin connector are clean. I just now tied the manual lever in the activated position with a string (I don't have a helper today) and listened to the wheels. I couldn't hear anything. Then I pressed my ear against each side wall and heard a buzz from each of the four, but I suspect the buzz could be getting transmitted through the scissor-type chocks. I guess I'll remove the chocks and try that again when it quits raining here. Any additional comments will be appreciated. Thanks again.