Trailer Brakes Pulse After Releasing Brake Pedal Using Time Delay Brake Controller

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Question:

Hi I have a Reese time delay style contoller on a 2004 F-150. Have towed a dump box style trailer with electric brakes with no changes to the truck, trailer, or controller for the last 10 years with no issues up until now. The trailer is only used on an occasional basis, perhaps 2 or 3 days per month, and very short trips, all being well under 50 km per trip. Trailer is stored indoors in a shop with a concrete floor when not in use, so corrosion on the trailer electrical system should not be an issue. The trailer brakes do not squeal, or otherwise make any noise during use. During the last few outings I have noticed that when you apply the brakes, and then release the brake pedal, that the trailer brakes seem to grab instantaneously and come on for a split second before releasing. The problem is consisent and happens every time you release the brake pedal. Adjusting the sensitivity adjustment on the brake controller does not eliminate the problem, it only seems to affect how hard the brakes are applied when this quick brake grab occurs. I have sprayed the truck and trailer plug / socket with electrical cleaner but this has not helped the problem. If I slide the button that allows you to test the trailer brakes with out applying the truck brake pedal, I can feel the trailer brakes come on independent of the truck, so I assume that the trailer brakes are working correctly. Any suggestions as to where to look for the problem?? Other than this, the trailer brakes work fine, and the adjustment on the controller still allows me to adjust just how hard the trailer brakes come on to match the load weight being towed. Thanks

asked by: Gord

1

Helpful Expert Reply:

The infrequent use of the trailer might be the issue. Or it could be that the system is fairly old. I would not count out corrosion because it doesn't take much moisture to cause some issues.

There is some testing you can do to determine if the problem is the brake controller or elsewhere. In the truck cab you will need to sever the blue wire several inches from the back of the controller. Then use a circuit tester such as # PTW2992 to test the end of the blue wire coming out of the controller. It should only have power when you apply the manual override or brake pedal. If it shows power at idle, then there is something wrong with the controller and it will need to be replaced.

If it tests fine, then reconnect the blue wire. Then move on to the truck side trailer connector. Many times, dirt or corrosion can cause a short in a trailer connector. Make sure the truck and the trailer side connectors are clean and free of corrosion inside and out.

You can test the brake output pin and it should only show power with the manual override. If it shows power any other time then there is a short somewhere between the connector and the brake controller you will need to track down.

If the truck side checks out fine then it could be the wiring to the brake magnets or the magnets themselves. Inspect the power wires to the magnets and look for pinched, frayed, or damaged wires and fix as needed. Make sure the ground wires are attached to clean and corrosion free bare metal surfaces.

You can visually inspect the magnets and if you can see the copper windings coming through the magnets will need to be replaced. It is also possible that the brakes need to be adjusted. This is much more common than you think. To further test the magnets you can follow the help article I have linked. I have also included some help articles on testing and troubleshooting brake controllers for you.

expert reply by: Michael H

1

Trailer Brakes Pulse After Releasing Brake Pedal Using Time Delay Brake Controller

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