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Race trailer lights giving me trouble


Broknarrow

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Standard 4 wire hookup and all lights on truck work fine.

On the trailer....

All marker/running lights work fine.

Turn signals work fine.

Hazards nada

Brake lights nada

WTF?

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I would always start with the ground. My trailer used to do this as well. What's happening is that there is enough ground to run one signal at a time, but once both lights cut on, there isn't enough ground so they just kinda fade in and out. Reground it at the tongue and it should solve the problem. If that doesn't work, check or reground the plug on the vehicle side.

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I would always start with the ground. My trailer used to do this as well. What's happening is that there is enough ground to run one signal at a time, but once both lights cut on, there isn't enough ground so they just kinda fade in and out. Reground it at the tongue and it should solve the problem. If that doesn't work, check or reground the plug on the vehicle side.

Makes sense...will try that. Thanks!

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+1 on grounds. I now go to the trouble of running a seperate ground wire to every light on the trailer. On the four wire connector, the white wire is the ground.

Do you have a set of jumper cables? Try connecting them to bare metal on the tow vehicle and the trailer. If the lights work right now, check the ground connections on the harness. Don't rely on a ground through the trailer hitch.

Make sure the white wire on the trailer goes to a bare metal connection on the trailer. Also make sure the white wire on the tow side is connected to a clean ground on the frame.

I should warn, the white ground wire is the only pin by itself. Example, on the car side, it will be the pin not insulated. If this wire is not going to ground, then it was wired different than standard. It will work, but most other cars won't work right with the trailer.

Also assuming that the trailer lights worked correctly at one time with this tow vehicle.

Some cars, like my old VW truck have seperate lamps for turn and stop lights. They don't work with a four wire without a adapter.

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