Troubleshooting Hopkins Wiring Harness to Flat Tow a 2018 Ford F-150

Updated 07/20/2020 | Published 05/10/2019

Question:

Installed Hopkins HM56009 on 18 f150. Works fine while driving truck. When towing running lights work fine. Brake and turns technically work but the driver side the top of the tail light lights up and on passenger side the bottom light lights up. When driving the truck both top and bottom light up at the same time on the same side. Why? Is the Hopkins bad? Did I install it wrong?

asked by: Clinton

Expert Reply:

We've actually heard of this issue before. You can thank one of our tech support guys for finding a simple solution for this. Even Hopkins wasn't aware of it.

First of all the harness is just fine and you didn't install anything incorrectly on your 2018 Ford F-150. Technically, you can just keep towing your truck as is and you won't have an issue other than the lights look weird.

Like you said, your F-150 has two bulbs in each tail light for the turn and brake lights; one on top and one on bottom. Each bulb has it's own connector that plugs into the truck's wiring and it's difficult to tell which connector is for which bulb when you find them. So Hopkins connector only plugs inline with one bulb on each side and when you install it there's no easy way to know which bulb, top or bottom, you're connecting with. So in short what's happening on your truck is that the Hopkins is inline with the top bulb on the driver's side and the bottom bulb on the passenger's side.

Like I said, there's nothing bad or illegal about leaving it like it is. If you just don't like it the easiest solution is to pick one side or the other and switch the top and bottom bulbs within the tail light assembly.

expert reply by: Charles S

Jorge L.

7/11/2020

I just installed the C56009 and it didn’t work. I connected the four way to my towing vehicle and tested before I continued with the installation. Any ideas?

Chris R.

7/16/2020

Can you tell me what specifically isn't working on the harness? Are any of the circuits getting power or just some? Also, what model tow vehicle did you install the harness on?

Jorge L.

7/16/2020

@ChrisR Its a 2018 F-150 Lariat 4x4. neither the brakes nor the blinkers operate.

Chris R.

7/20/2020

@JorgeL Thanks for the info! I think it's possible that there's either a blown fuse under the hood of your F-150 (check your owner's manual for appropriate fuse locations tied to the "trailer turn/brake signal circuits") or the converter for the Hopkins # HM56009 is bad.