Troubleshooting 2018 Ford F-150 W/ 4-way Connector That Has Power But Doesn't Power Trailer Lights

Updated 07/07/2021 | Published 07/06/2021

Products Featured in This Question

Curt T-Connector Vehicle Wiring Harness with 4-Pole Flat Trailer Connector

(193)

$69.70

Adapter 4-Pole to 7-Pole and 4-Pole

(660)

$61.81

Plug-N-Tow (R) Vehicle Wiring Harness

(17)

$27.92

Question:

Hi, I have a 2008 F150 and when I hook up my boat trailer the lights wont work. I have power at the bumper, I put a low voltage tester on the 4-pin and it reads 11-12v. I have used other vehicles to test and the trailer lights work perfectly. Here is also were I am confused, I was looking at a new 4-pin/7-pin socket combo, that should plug into the existing wires, but it has a round socket and the truck has a flat/rectangular plug connected higher up on the frame. any help would be greatly appreciated.

asked by: Walter M

Expert Reply:

Since your 2008 Ford F-150 has a 4-way connector and you tested it and it has power but your boat trailer lights are not working I would check that the connector does not have corrosion/debris on or in it causing a connection issue.

It sounds like your truck came with the factory 4-way connector, and if that is the case then it does not have the correct connector to just replace the connector with a 7-way. Instead you would need to use the # 37185 which will plug into your factory 4-way connector. For the remaining connections you will need to find the rectangular connector on the frame rail as shown in the included picture and cut the blue and orange wires from the factory connector. The orange wire is the 12v power wire and will get connected to the black wire on the 7-way connector, and the blue wire is the brake output wire and will get connected to the blue wire on the 7-way connector.

Now if your 4-way connector is bad or has internal corrosion causing it to not work correctly you will need to replace it with the Plug-N-Tow (R) Vehicle Wiring Harness # 40185.

I included videos of the products mentioned for you to take a look at.

expert reply by: Samuel C