Troubleshooting Running Lights on Trailer Not Working When Connected to a 2001 Ford F-150

Updated 05/13/2010 | Published 05/12/2010

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Question:

i just bought a camper so i upgraded my trailer wiring on my truck to a 7 way plug using 118242. i plugged it in and all i can get is brake lights and turn signals on my camper. all the lights on my truck are functional. i had my dad hook his 2004 f150 up to the camper and when he plugged it in all the lights worked. i cleaned the ground for the harness this morning and theres no change

asked by: Jake

Expert Reply:

If your 2001 Ford F-150 is equipped with a factory 4-Way trailer connector, the Tow Ready Custom Fit Vehicle Wiring, # 118242, should work. There are a couple of things you can check. First, there are a few fuses that need to be installed if you have not done so. I have included a link to the instructions below. The first few steps address the fuses. Also, you can check to see if any fuses are blown. A tow package running light fuse might be blown and need to be replaced.

Also, check that the running light wire functions properly at the 4-Way connector. If it does not work, then the wire is most likely broken or loose somewhere behind the plug.

If your truck did not come with a factory 4-Way trailer connector, then the 118242 harness will not work. Instead, you will need to install a 4-Way, like Tow Ready Custom Fit Vehicle Wiring, # 118344 which installs in line with the vehicles taillights. You would then plug the 4-Way into the back of Adapter 4 Pole to 7 Pole and 4 Pole, # 37185. The white wire is for the ground, the blue wire is for the trailer brakes, the black wire is for a hot lead coming back from the battery, and the purple wire is for another auxiliary function (usually reverse lights).

To complete the install of the adapter, there are a couple of wires that you will need to test with a circuit tester like # PTW2993 Before the plug where you initially installed the 118242, look for a blue and orange wire. Blue is electric brake output. If you have a brake controller, have someone engage the manual override. The blue wire should carry a signal when the controller is engaged. If it does not, find the wire that does and attach it to the blue wire on the 37185.

Next, turn on the key and find the wire that carries a constant 12 volt signal (it could be orange). Attach this wire to the black wire on the 37185 harness. The purple wire will connect to a reverse light wire behind one of the taillights. I have included an FAQ article on wiring a Ford Truck that should help.

expert reply by: Michael H