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Ugh...wiring issues.


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Here is the story. We have 5th wheel and I had to change the 7 pin because it was a little long and one time slipped out of the jury rigged method I had to hold it off the ground. I replaced it and realized that the tails lights don't work. Truth is we never towed it at night and never had a reason to check to see if they worked.

I have checked and rechecked the wiring and it is all good by the book. I have tried the 7 pin in both my 3/4 ton and my wifes trail blazer and neither work. I have also traced the wire for the tail lights and ran power directly to that and the tail lights etc then it works fine. I tried running power from the tail lights to the other side of the where the 7 pin plugs into and the tails lights come on, but then the right side blinker doesn't work.

I did notice the yellow wire on the RV side doesn't exist and it was cut back on the old 7 pin. Like I mentioned earlier I am not sure if the tail lights ever really worked.

Anyone got any ideas?

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Everything else works fine, blinkers brake lights and if I power them directly they power up fine. Ground was the first thing to cross my mind too, but there is also a direct ground wire in the plug and it does fail with 2 vehicles.

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how are the grounds?
I'm with EyeChsr. You need to check the ground at the light fixtures in the back. I have had more then one trailer with good wires all the way to the back and then the light fixtures themselves were corroded at the gound.
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I would start by using a test light to verify that all the pins that are supposed to on the vehicle end have current when they are turned on. First by using a known good ground, then again by using the ground pin in the connector. If that all checks out, move on to opening up the trailer connector, plug it in and test for current at the correct tail light pin. Verify that the pin for the tail lights corresponds to the proper pin on the trailer end. My guess is that either a wire pulled out of the connector pin or its installed in the wrong one.

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Here is the wiring for the way mine has been wired up.


Here is another view.


If I put 12 volts to the green I get tail lights and marker lights like I should. Straight through the plug I don't. I found an article stating there are trailering fuses under the hood by the battery, but haven't had a chance to check on it yet.


There are about 5 fuses for the trailer harness, Trailer Back up,Trailer left turn, Trailer right turn, Trailer Brake, and Trailer hazards. They are located in the underhood fuse box on the Drivers side of your motor.

On my 2003 Silverado, the Trailer left/stop and Trailer right/stop fuses are located in the fuse panel just inside the driver's side door. (Not sure about the trailer brake or hazard fuses.....I wasn't having problems with those smile.

There is one additional fuse for the trailer harness. The 15A fuse for the trailer running lights is located in the fuse panel under the hood, next to the battery. The fuse is labeled "Trailer Park".

Read more: http://wiki.answers.com/Q/Is_there_a_fus...o#ixzz215SjXh57

Read more: http://wiki.answers.com/Q/Is_there_a_fus...o#ixzz215QvIhPQ

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Ok good, thats why I said I'd start by using a test light to verify that the tail light pin on the vehicle has current when turned on.

It could very well/likely be the fuse, but there may be a problem on the trailer causing it to blow on both vehicles unless its just a coincidence.

Here is a pic of which fuse you need to check. As you are standing next to the fender it is the 15 amp mini fuse furthest left and furthest away from you. (see arrow)


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Both vehicles also tow the boat, so I may have a short on the boat too. When you don't normally tow after dark you don't see these things.

Thanks for the photo. I will update if that is the issue.

Thanks to all the input.

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