All lights on the trailer work as well. When i slide the trailer brake controller the brake lights do come on but no braking happens. Trailer Wiring Guide Boat Trailer Lights Trailer Wiring Diagram Utility Trailer This is a system that automatically brakes your travel trailer if it ever detaches going down the road. Trailer brakes not working on truck . If there is a bad ground connection the trailer brakes will not work. I have tested my brake controller (at the controller and on the truck side of the 7 pin connector) and all voltages are good. Next, check the brake controller wiring. All the running lights and brake lights work but there is no response from the trailer brakes. You can test the brake output pin and it should only show power with the manual override. Picked up my tt with my new truck for its first tow and the trailer brakes aren't working. If the tractor is not giving service air. The brakes on the trailer work fine when hooked up to other tru...