Troublsehooting Brake Controller That's Not Reading the Trailer

Question:

Can bad magnets cause the controller to not connect to the trailer? When using the brake or lever I have voltage on the blue wire on the trailer.

asked by: Jacob

Expert Reply:

It's more likely you'll show a short circuit or an overload error code on the controller, which could depend on the brake controller you're using, but worn brake magnets would certainly prevent the controller from 'reading' the trailer.

Let's look at the easiest fixes first, though.

Examine the connections for the brake magnets behind each brake assembly. There are two wires exiting each brake assembly. One wire should be grounded to the trailer frame, this connection should be secure and corrosion-free. The other wire should tie into the brake circuit, which is typically a blue wire. If one of your grounds has come loose or the wire has broken, it could explain the problem you're having.

If that looks okay, check your trailer connector on the vehicle and on the trailer to ensure it's not corroded or damaged. A small amount of green or white corrosion on the pins could prevent the controller from reading the trailer.

If that all checks out okay, you'll need to pull your brake drums and examine the face of the magnets that ride against the armature surface of the brake drums. If you see any of the copper windings showing through the face of the magnets, the magnets or brake assemblies themselves will need replacement.

I'll link you to our Brake Controller Troubleshooting article which you might also find helpful.

expert reply by: Mike L