Troubleshooting 4-Pole Flat Trailer Connector on 2005 Ford Explorer Sport Trac

Question:

1 I have no power coming out of the 4 way flat vechicle connector on the truck when I did open it up it was full of a green corosive which I cleaned out and sprayed WD 40 inside. The plug is still not working and no power and the fuse is good. What else can I check on this vechicle.2 I have a second question on the wiring harnes a 5 way flat connector there is a red wire on it where does this connect too. Is this an Auxillary power that can be used for a break away box later.

asked by: Alvin

Expert Reply:

For the 4-way, I would recommend using a circuit tester like part # PTW2993 and testing the wires before they reach the connector. This will rule out the connector itself as being bad.

If the 4-pole connector is an aftermarket addition, trace each wire leading from the connector to ensure that they are still connected. If the trailer connector is factory installed, it might be a blown fuse. The fuses that protect the towing circuits are usually located under the hood, it is possible you missed them when you looked before.

A 5-pole Flat trailer connector is typically used on boat trailers. The extra wire is tapped into the reverse light circuit on the vehicle. When the vehicle transmission is shifted into reverse, the surge or hydraulic coupler on the trailer is disabled so that the trailer can be reversed without the brakes being activated.

Any trailer that needs a break away system will have electric brakes. The vehicle towing that trailer will need to be equipped with a 7-way trailer connector, as well as a brake controller to actuate the brakes.

Using part # 37185 would convert your existing 4-pole to a 7-way, with the remaining wires connecting as follows:

White ground wire attaches to clean metal on vehicle
Blue wire attaches to blue output wire on brake controller
Black wire attaches to positive battery terminal via 40 amp inline circuit breaker (part # 9510)
(This circuit would be used to provide 12-volt power to a break way system)
Purple wire attaches to reverse light circuit on vehicle (if needed)

For a brake controller, you cannot go wrong with the Tekonsha Prodigy P2, part # 90885. The P2 is a proportional controller, that when properly adjusted, will ensure that the trailer and the tow vehicle brake at the same rate. This leads to safer, more controllable braking.

I have provided links to the products I have recommended, as well as links to our Brake Controller FAQ page and other helpful information.