Trailer Brake Controller has Possessed a 2003 Ford Explorer Causing Lights and Door Locks to Cycle

Question:

Brake controller is 6 years old. Recently all lights, brake, turn signal, etc. Have been operating intermittintly. Ive had all wiring and both the trailer and explorer plugs replaced. Brake controller stays on,tail lights stay on, door locks cycle by themselves. Mechanics say that the brake controller has to be the problem. My brake controller is hard wired in. If I purchase a new brake controller and it comes with the easy install plug, do I clip the wires and just connect to the old wires.?

asked by: Craig S

Expert Reply:

Brake controller plug and play harnesses are sold separate from the controllers themselves. So if you just wanted a brake controller like # 39523, yes, you would just cut off the plug end and wire it to the existing wires (provided the existing wires are all in good working order). Does the problem go away when you unhook the controller?

I am not sure what could have gone wrong with a brake controller to make the power door locks cycle. That is probably one of the stranger things I have heard as far as brake controller problems go. It does sound like at some point there was definitely a short and/or ground issues, most likely brought on by corrosion that caused some of these issues.

Starting on the 2003 Ford Explorer I recommend taking a close look at all of the wiring to the trailer connector. You will be looking for corrosion and broken wires with exposed copper strands touching bare metal. Given the age of the vehicle it is not likely to be too bad off, unless you live up north where the winters can be harsh.

Since you hardwired in the controller does that mean that the Explorer did not come with a factory 7-Way trailer connector? If that is the case I really do recommend starting from scratch on the vehicle side so as to avoid hunting down gremlins that may not want to be found.

You would start with a 4-Way wiring harness, # 118344. Then normally I would say use # ETBC7 for the 7-Way. However, you recently replaced the 7-Way so it is most likely in good working order, aside from the current issues. So instead I recommend making the attachments as needed from the new 4-Way and using new wire for the 12 volt power and brake output wires that go to the front of the vehicle. You can use wire # 10-2-1 sold in 1 foot increments.

Then you will replace the brake controller with a solid, reliable model like the P2, # 90885, or the Primus # TK90160. Then you can follow the ETBC7 instructions, linked, to perform all the hardwire parts.

On the trailer side you will inspect all of the wiring looking for breaks and make sure all the grounds are attached to clean and corrosion free bare metal surfaces. Check the pins on the connector to make sure they too are clean. You can also follow the FAQ I linked to test the brake magnets. If there is a problem on the trailer or in the wiring leading to the controller, this problem will likely happen again.