Trailer Turn Signals and Brake Lights Stopped Working with 2005 Ford F-150

Updated 07/17/2020 | Published 11/01/2015

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Question:

I have a 2005 ford f-150 and a landscaping trailer that I installed electric brakes on everything worked great for a while then the turn signals and brake lights stop working the other lights work fine maybe you can help me. Thanks

asked by: Rick S

Expert Reply:

The first thing to check is the trailer connector on your 2005 Ford F-150. With the trailer disconnected use a circuit tester such as # PTW2993 to test the vehicle side connector while someone sits in the cab of the truck and activates the turn signals and brake lights. If there is power at the truck side connector, then the problem is on the trailer.

Make sure that the truck and trailer side connectors are clean and free of corrosion inside where the wires attach and outside on the pins. Inspect the wiring front to back on the trailer and repair as needed. Also make sure the main trailer connector ground and the grounds for all of the lights are connected to clean and corrosion free bare metal surfaces.

If there is no power at the vehicle side connector then the issue is on the truck side. Make sure the wiring is intact and repair as needed. There could also be a tow package fuse that is blown and needs to be replaced. In the fuse panel the fuse for the trailer right turn signal/brake light is in location 36 and the left side is location 42.

expert reply by: Michael H

Billy

7/8/2020

i have a 2012 ford f150 and a new bass tracker boat and trailer -tail lights and running lights work but no brake lights or blinker lights

Chris R.

7/13/2020

Is it the turn/brake lights on both sides of the trailer or just one? Either way, I would start by testing the connector on your F-150 to see if you're getting power there. This will quickly tell you which side the issue is on (if you are getting power on the turn/brake pins the problem is somewhere on the trailer - if not, you know the issue is on the truck). If it's a truck issue, the first place I would check is the fuse box under the hood. Look at your owner's manual for the appropriate fuse locations and see if they need to be replaced. On the trailer I would make sure the main harness ground is still securely attached to a clean, bare metal portion of the frame. Let me know what you find and we can keep troubleshooting if needed.

Billy

7/13/2020

hooked another truck to trailer and they work fine and did not find any blown fuses seems to be at plug

Chris R.

7/17/2020

The plug itself may just be bad. You can try replacing it with the Curt # C55774. To verify this is the issue you can test the wiring BEHIND the existing 7-Way connector to see if you get power on those circuits with the turn signals or brake lights on.