1999 Ford F-250 No Trailer Running Lights Even After Replacing 7-Way Connector

Published 01/29/2020

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Question:

Carla, las luces tiene algún relay que puedan estar dañado? Carla, do the lights have some type of relay that could be bad?

asked by: Reinaldo

Expert Reply:

I know you said you checked the fuses, but on your 1999 Ford F-250, the Power Distribution Box and Trailer Tow Relay Blocks are located in the engine compartment near the brake master cylinder, not to be confused with the Fuse Panel located below and to the left of the steering wheel.

There is only one fuse that is tied to your trailer running lights inside the Fuse Panel:

Fuse Location 28 - 10 amp - Brake Shift Interlock, DRL Relay Coil, Speed Control Module, Backup Lamps, Trailer Tow Backup Lamp Relay Coil, Electronic Shift On The Fly Hub Lock Solenoid

Below are the fuses that are tied to your trailer running lights inside the Power Distribution Box:

Fuse Location 4 - 20 amp - Trailer Tow Backup Lamps, Trailer Tow Park Lamps
Fuse Location 8 - 15 amp - Trailer Tow Electronic Brake Illumination, Park Lamps, Trailer Tow Park Lamp Relay Coil

If you checked all these locations and the fuses are good, you'll need to use a circuit tester like # PTW2992 to test the pin on your new 7-way at the 11 o'clock position, as shown in the attached diagram. If you get no power there, it's likely some other wiring issue on your truck. Otherwise, if it's active, the issue is going to be somewhere on the trailer side, in which case, please let me know so I can continue troubleshooting with you.

I attached a link to our Trailer Wiring article for you to check out as well.

expert reply by: Carla M

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Reinaldo

1/29/2020

Carla, las luces tiene algún relay que puedan estar dañado? Carla, do the lights have some type of relay that could be bad?

Carla M.

1/29/2020

Yes, as you can see in the third attached photo with the red arrow, there are two trailer tow relays. The Trailer Tow Back Up Lamp Relay is in position # 38 and the Battery Charge Relay is # 39. You will find these in a separate smaller relay block, next to the Power Distribution Box and the shift on the fly relay block. I've attached an additional photo to help you identify it. The trailer backup light relay is the one closest to the firewall.