Troubleshooting Trailer Brakes Not Working on New Trailer

Question:

Several years ago I bought a wiring harness from etrailer for our camper and horse trailer. Its working fine. But now Ive inherited a flatbed trailer and the trailer lights do not work with it. Same 7 pin wiring, just no green light on my controller. Have done a trailer check for bad grounds but so far nothing. I get 12 volt power all the way to the brakeaway switch but after the brakeaway battery, nothing. The battery is shot, but I know it only for emergency brakes. Does the problem sound like it may be in my brake magnets or a ground at the brakes? I am baffled at this point. Also, could the brakeaway battery send a message, therefore not giving me a green light? Thank you,

asked by: Craig

Expert Reply:

I recommend first testing the 7-Way connector at the rear of your tow vehicle with a circuit tester like # PTW2993. You can have somebody run through the functions inside the vehicle while you test each pin. You will want to make sure the brake controller is set to its highest setting and apply the manual override to test the brake pin location (5 O'clock position). If you are receiving power on all the circuits, then you know the issue is on the trailer side.

Next, check to make sure both the vehicle and trailer side connector are free of any dirt or corrosion, simply cleaning out as needed. Since you already looked for ground issues, I then simply recommend going along the trailer wiring on your trailer, inspecting the wires for any exposed, corroded, bent or damaged sections - replacing if needed.

As you mentioned in your question, you can also take a look at the brake assemblies to make sure they are properly grounded, as its possible that this is the issue.

The green light on your brake controller will only come on when the controller senses the load from the brake magnets on your trailer. If the brakes are not operating as they should, the green light will not be activated. So if everything checks out fine with the trailer wiring and ground connections, you can test the brake magnets on the brake assemblies. I have attached a great article that explains exactly how to do this

If you are still unable to resolve the issue, please let me know and I will be happy to look into this further.

expert reply by: Chris R