Tandem Cargo Trailer Brakes Locking Up On a 2004 Ford F-250 Without Brake Controller

Question:

I have a 16foot tandem cargo trailer. I have a 2004 F250 with a prewired trailer connector. Used this trailer first part of September with no problem whatsoever. Went to use it a few weeks ago and the least little push on the brake pedal locked up the trailer brakes. What should I look at to be the problem and cause of this? Does not have a brake controller.

asked by: Carl M

Expert Reply:

Trailer brakes activate with electric signal. Your brakes received a signal telling them to lock up so we have to find out why the signal went there.

The most likely culprit is corrosion. Since your trailer has been sitting for a while it has had a chance for corrosion to build up. Check your trailer connector for a whitish/greenish substance in or around the pins and the wire. Corrosion expands as it goes unattended and is pretty wicked because it can actually transfer signal from the corroded pin to an unsuspecting pin.

If your brake light pin is corroded it could transfer signal to the brake controller pin and activate the trailer brakes when you press on your brake pedal which results in your trailer brakes locking up. (These pins are right next to each other).

If your truck/trailer has a breakaway switch, that would be the next item to check. Corrosion may have built up in your breakaway switch and inadvertently activated as you pressed on the brake pedal which locked up your trailer brakes.

Next I would check the brake magnets. Before you test the power wire, make sure the ground wire is grounded properly on a clean, bare, metal surface. Check for corrosion on this ground connection as well. Corrosion can negate the ground.

Use a circuit tester like # PTW2993 to check the power wire to the brake magnet on the wheel with the locked-up brake. If there is no power on the wire, then the problem is most likely mechanical in nature involving a broken brake assembly spring or an actuating arm that got some road debris wedged in it.

If you do not have signal on your trailer brakes then you know it is a mechanical problem with your trailer brakes. Your trailer brakes could simply need an adjustment or you could have a broken brake shoe. You will know as soon as you jack up the trailer to inspect the brakes.

The quick solution that will not tell you why it happened but will prevent it from happening again is to disconnect the brake magnet wires.

I have attached two FAQ articles covering testing brake magnets and connector wiring. If you find that you will need to replace your brakes I have also attached a link to the brakes we offer.