Troubleshooting Ford F-250 Combination 4-Pole/7-Way Wiring for Boat Trailer

Question:

Ive got the 4 and 7 pin connector plugs on the back of my 2016 Ford F250. No trouble with the 7 pin, but when i hook up my boat on the four pin, no trailer connected warning light on my dash nor do the lights work. Wheres the switch that Im suppose to flip?

asked by: Bob T

Expert Reply:

With the factory-installed combination 4-pole/7-way trailer connector on your 2016 Ford F-250 there is no switch to change between the two plug formats. Both the 4-pole and the 7-way will be active at the same time and can be used together, say for example with the 4-pole connected to a light bar or slide-in camper and the 7-way handling your towed boat trailer's connection.

The lighting signals that are carried on the 4-pole are the same as those included in the 7-way, so if the lights work with a trailer connected to the 7-way they should also work on the 4-pole.

If your truck has a factory integrated trailer brake controller the error message, you are seeing could simply be that the truck is telling you it does not sense a connection to a trailer brake circuit. This would be normal since the 4-pole format does not include a brake circuit, only lights.

I suggest you separately test both the vehicle 4-pole connector and the boat trailer. First, get a circuit tester like # PTW2993 and apply the tester to one circuit at a time while a elper activates the appropriate function on the truck. You can refer the linked article on trailer wiring to see which function's signal should appear on each 4-pole contact. Also check the connector contacts for discoloration or corrosion that could be blocking signal transmission.

Next test the trailer 4-pole wiring by directly connecting the truck battery or a well-charged spare to the three circuits on the trailer's 4-pole. Each circuit, left stop/turn, right stop/turn and running lights, should activate with this direct power input. if the trailer lights do not function with this direct power input then focus on the trailer as the cause for the issue. Again, check for corrosion or discoloration on the 4-pole contacts and particularly for a loose main ground wire at the trailer frame. The main ground must make solid metal-to-metal contact on a clean surface that is free of rust, dirt, grease, paint and primer.

An application of dielectric grease like # 11755 will protect your contacts from corrosion and and help keep your connections reliable.