Troubleshooting Weak Brake Output From Truck When Towing toyhauler

Question:

Hello, I need some expert advise on how to troubleshoot my trailer brakes. My toyhauler brakes are very weak. Pushing the manual lever on the brake controller to max boost yields little recognizable increase in stopping power. Ive done the voltage checks listed below and have no idea where to start as Im ping a little voltage everywhere. The truck battery voltage: Measured neg to pos on the battery and pos to chassis = 12.5V Voltage at the truck 7way plug: brakes only = 3.8V brakes with manual boost lever maxed = 11.4 Voltage at the trailer junction box on the king pin: brakes only = 2.4V brakes with manual boost lever maxed = 9.2V Voltage at the trailer tires: brakes only = 1.5V brakes with manual boost lever maxed = 8V These checks leave me confused as to where to even start as Im losing voltage at each test point. Any advise is much appreciated.

asked by: Jason V

Expert Reply:

It sounds like your brake controller is not giving you the output it should. If you are parked and you use the manual override to the max it should be near 12 V.

You can sever the blue output wire coming form your brake controller and check the wire while using the manual override. If it has a very low reading as you said, the brake controller may be bad and need to be replaced. If that is the case I recommend part # 90195. This is one of our most popular because it is easy to set up and operate.

If the brake controller output is reading around 12 V when the manual override is used, then you will want to check the trailer connector pins. Make sure the trailer connector on the truck and on the trailer are free of dirt or corrosion. With the trailer unhooked check the brake output pin when using the manual override. If you get a good reading move to the connector on the trailer. If you see a drop, you will want to check the ground on the truck side and on the trailer side. Make sure your ground is securely attached to a clean bare metal surface.

expert reply by: Jeffrey L