Running Lights Function but Brake and Turn Do Not on a 2006 Carlson Utility Trailer

Published 08/09/2010

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Optronics Combination Trailer Tail Light - 6 Function - Incandescent - Red Lens - Passenger Side

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Hook Probe Circuit Tester

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Question:

decided to get new wires. Hooked them all back up, still parking lights, no brake or turn, its got me....can it be off the truck, don't make sense thanks for the help.

asked by: Patrick

Expert Reply:

It could definitely be a ground issue. Since you were able to duplicate the same result with the same trailer on two different vehicles, than it is pretty safe to say the problem is somewhere on the trailer.

I would start with the trailer connector and work back. Trace the ground wire, usually white, back from the connector. Make sure it has a good clean connection to the metal of the trailer frame. Paint, rust and corrosion can insulate connections so make sure it is good metal to metal contact.

The grounds at each light are not as likely since you have parking lights, but it would be worth checking those as well.

Next, I would go back to the trailer connector, and trace the brake/turn wires, usually yellow for left and green for right. Follow them back along the trailer checking for nicks, frays or corroded connections.

Finally, check the bulbs. Trailer bulbs can and do go bad from time to time. They may just be burned up. It is also possible that you have dual filament bulbs. One filament does parking lights. The other filament is brighter and handles brake and turn. If your bulb has two filaments and one is broken, replace it.

I imagine one of these 3 sources is the problem. If not, write back. Be sure to include any more info you find while checking the above items.

expert reply by: Patrick B

Patrick

8/9/2010

decided to get new wires. Hooked them all back up, still parking lights, no brake or turn, its got me....can it be off the truck, don't make sense thanks for the help.

Patrick B.

8/9/2010

It could be off the truck, but if you got the same results on a different tow vehicle, it makes the truck much less likely. Check the power distribution block or fuse block of the truck. If your truck came with the trailer connector you are using, it would have dedicated tow light circuits with their own fuses. Check to see if you have any blown tow circuit fuses. If you want to positively determine if the truck is the source, use a circuit tester like part # PTW2993, and test each of the contacts to make sure they are functioning properly. I have included a link to an FAQ below that will go over this in more detail with photos. It is also possible that the trailer connectors are corroded internally which can insulate connections. This is more likely with a round trailer connector like a 7-Way, 6-Way or a 5-Way round. The flat 4-Pole and 5-Pole connectors do not really have space inside for moisture to accumulate and build corrosion. If your connector can be taken apart, you may want to pull them open and give them a good cleaning with some electrical connector cleaner.