Brake Controller Does Not Work with Hazard Lights on a 1987 Ford F-350
Question:
Ive had this truck with the 5504 controller for over a decade with no issues. A few years in there I was pulling a trailer daily with no problems to report. The past few years the truck hasnt seen much use so I dont know if that may be a factor. Currently the trailer brakes wont activate on two trailers. When checking the circuits I found everything at the pins 6 pin and 7 pin connections have power where they are supposed to except the brake pin on both has a low current to it when the flashers are on. It does not do this with any other combination of lights on. I could not read the voltage as it was flashing. I was using a test light which flashed dim compared to a fully live cicuit. The small red LED on the controller would flash as well. The trailer brakes make a slight buzzing sound in time with the flashers and continuous when only brakes applied. I disconnected the brake light circuit to remove it from the equation. The flashers on the truck flash slower when the trailer is hooked up. Im assuming because the brakes are drawing some of the current, but not enough to engage the brakes. Without disassembling anything, I did not find any corroded connections or chafed wiring which could cause a short.
asked by: Red
Expert Reply:
It is possible that a pulse preventer # 5501 will at least solve part of the problem. It would be required when the brake control unit must be set to higher output levels and driving with hazard flashers is necessary. But the Pulse Preventer is not necessary for vehicles that have a different bulb for the stop and turn signals (amber turn signals).
It could be that you need to make new connections between the brake controller red wire and the brake switch on the truck. Or it might be time for a new brake controller. To determine if the brake controller is a problem there is some testing that you can do.
Brake controllers do send back a minimum amount of voltage to check for a connected trailer but it should not be enough to activate the brakes.
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 # PTW2993 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. 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.
