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Trailer Blinker and Turn Signals Only Work on One Side


Hello, I had to replace the plug on a trailer and the recepticle on a 2007 Ford E150. There was no existing plug to copy the wires. There was on the recepticle. That only had 4 wires and the plug side has 7??? I looked up the schematics and found traditional wiring was the route to go since it did not have a purple wire. I hooked the yellow to the middle for backup lights, I believe I used Brown for one side turn siginal and red for the other. I am not getting a turn siginal or brake light on one side. I do have running lights. The right side works perfect. Ive cleaned both grounds on the tongue and it appears there was one on the back of the trailer. It is an enclosed trailer so I cant really trace the wires without pulling it apart. I did not check fuses since I believe they would both be out then. I personally think I wired it wrong but not sure. Any help would be appreciated. Thank you


Expert Reply:

Since it sounds like you were trying to match up colors during your install I believe you are correct that you wired it incorrectly. Although there are common wiring colors, there are no rules saying that everything has to be wired using any specific colors. This goes for both vehicle and trailer side. If you connect wire colors instead of checking their functions you could end up with an incorrect wiring system.

What I recommend doing is using a Circuit Tester # PTW2979 to test the function of each pin on the connector on your tow vehicle. You will then want to use a 12V power source, like the battery from your tow vehicle, and test the pins of the connector on your trailer. If the signals of the pins on your vehicle side do not match those on your trailer side then that was your problem.

Another thing to note is that if your trailer has wire running to all 7 functions on the 7-Way then that means it has brakes. When a trailer has brakes they need to be used for safety reasons.

If you can let me know what functions your trailer has and what functions that your 2007 Ford E-150 sends then I will be more than happy to help you make sure everything is activate on your trailer side.

I have also attached a helpful article on wiring that you can use as a reference.

expert reply by:
Jon G

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