Troubleshooting Brake Lights And Wiring On 2003 Ford 250 Super Duty
Question:
I do not have a owner's manual for my 2003 Ford 250 Super Duty V10 Titan. So I don't know which fuse to look at or for to check relays. Everything works on my trailer except brake and turn signals and all the wiring looks good on the trailer. I replaced plug on trailer and got the same problem. Can you tell me which fuse and relay to look at and how to get my spare tire lowered, the key no slot to use the tool to lower it.
asked by: Scott A
Expert Reply:
There are a few troubleshooting steps to help you figure out why your brake lights and turn signals are not working.
I would start by making sure that there is not any corrosion or debris blocking your connection points. If they are clean or still not working, I would check your grounding connections. Make sure your grounds are firmly connected to a clean, bare metal surface.
Before jumping to fuses, I would make sure the issue is definitely the tow vehicle side or the trailer side (I know you have already worked on this). Use a circuit tester like Item # PTW2993 to check each pin on the connector on the back of your vehicle. If the vehicle side checks out, then you know for sure that the issue is on the trailer side and vice versa.
Next, I would jump to the fuses if you still had problems since you have already checked several other possibilities. I would check the Trailer Towing Light Relay fuse in the junction box under the dash. This 20-amp fuse is in location #6. Another fuse to check is the 30-amp Trailer Tow Electric Brake fuse in location #101. I would also check the #305 relay location because it is related to trailer and towing functions. If any of these are bad then might be why brake lights and turn signals not working.
If you still have having issues after all of these checks, you will need to inspect the wiring coming out of the connectors for your brake lights and turn signals. Trace the brake light and turn signal wires and see if you find any damaged, pinched or disconnected wiring.
I checked in the owner's manual and lowering your spare tire requires a special key and an extension. Assemble the extension and and hook into jack handle. Attach spare tire lock key to jack handle, fully insert jack handle through bumper hole into guide tube. Key and lock will engage with slight push and counterclockwise turn. Turn counterclockwise to lower spare tire. If you do not have all the pieces or need more help, I would visit a local Ford dealer.
To help in the future, you can get access to a PDF of the owner's manual at www.ford-f250.com.
If still having issues, let me know and we can keep troubleshooting until we find it.
I have attached a few articles regarding trailer wiring that might help.
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Dakota L.
7/13/2020
I have an 03 f250 7.3L 4x4 and my center mount brake light works but the rear ones don't turn signals work good 4 ways work all but the center mount brake lights don't