Troubleshooting Weak Trailer Brakes With OEM Brake Controller

Published 04/20/2022

Question:

Hey guys, have very weak trailer brakes, and I cannot figure out the issue. Trailer brakes are very light, even when turned all the way up. Truck can idle through the brake, but there is a slight pull when using the controller pads I have a factory brake controller in an f250. There is just the gain adjustment. All brand new brakes and drums. Adjusted to where I can spin the wheel but it stops right when I let go of the tire When the emergency pin is pulled on the brake away chain, still weak. Redid the connection in the main trailer junction box. Can verify all four brakes are getting power, it’s just weak. The grease seals are not blown out. Get 12/13 volts using a multi meter at the harness of the truck, s down to 11 in the brake section. I have hooked up and unhooked every combination of the individual brakes in the back. I even ran new wire through one axel. All new connections/joints, thinking an old connection may have been bad. Disconnected the back axel and tested just the front. Get 12v when one wheel both right or the left is hooked up, get 11v when both right and left are hooked up. No wiring faults alerts on my truck except when I unhook a connection normal. Grounds should all be good. No idea what to try. At this point, I would like to try a different trailer or different truck on my trailer. I had a different trailer and same truck without this issue. So thinking it is the trailer. But no idea what it could be Are those volt readings normal? I assume there would be some . Can the volts be high but the amps too low? Should I have the brakes adjusted tighter?

asked by: Brock S

Expert Reply:

The best thing I can recommend to try is to check if your brake controller is even working via amp draw.

This will allow you to see if your controller is working, and how much your magnets are drawing when fully activated.

What you'll want to do is use a multimeter like the Digital Multimeter with 42" Long Test Leads # PT29ZR with the clamp on attachment and set the multimeter to DC.

Next clamp onto the brake lead on the driver side of the trailer where it starts back to the brakes. Then, have someone activate the controller while you're monitoring the multimeter.

If you're seeing somewhere from 10-12 amps then your electrical is fine, and the problem is more than likely mechanical in terms of a brake adjustment.

If you're not seeing an adequate amp draw, then you're issue is going to be with the electrical, and you'll need to check your connections are clean and secure.

Loose or dirty electrical connections can make your brakes weak or not function properly.