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Troubleshooting Dim Running Lights and Both Turn Signals Flashing on Trailer


running light work but seem very dim more than usual nearly invisable if in the sun . When either turn signal or hazards put on all light flash. Break lights seem to work but again very dull. Checked fuses in trailer all seem to be intact. Likewise in tow vehicle.


Helpful Expert Reply:

It sounds like you might have two separate issues going on simultaneously.

First, if the lights are very dim it is usually because the necessary amount of voltage isn't reaching the lamps. Since this is occurring on more than one circuit, I'd guess that the problem is most likely a build-up of corrosion on the trailer connector on the vehicle or the one on the trailer. Closely examine the pins and sockets. If you can see white or green corrosion, it's likely that the corrosion is restricting the amount of voltage actually reaching the lamps. Fine sandpaper or emery cloth could be used to clean the corrosion. Using some dielectric grease like # 11755 will prevent water from getting into the connection going forward. Also, check the connections where the trailer connector ties into the lighting circuits on the trailer. Sometimes these connections can become loose over time. The best way to secure these is by soldering them, then using heat-shrink connectors like # DW05451 to protect the connection from the elements.

The issue you're having with the turn signals flashing at the same time is a ground problem, it's a classic symptom. Check the main ground on the trailer tongue, make sure this connection is secure and is not corroded. Make sure each trailer lamp is either grounded by its direct connection to the trailer frame or by wire that's attached to the trailer frame. You also might have a poor ground connection on the vehicle side, make sure the trailer connector is properly grounded to the frame of the tow vehicle.

Once you get the issues straightened out, you might consider going with LED trailer lamps. LED's draw a fraction of the power of incandescent lamps, they draw a tiny fraction of the power and they're much brighter than incandescent lamps. I'll link you to our selection of LED trailer lamps.

I've linked you to a couple of help articles with more information on trailer wiring. I hope you'll find it helpful.

helpful expert reply by:
Mike L

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