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The Audi Doctor
The Audi Doctor, Technician
Category: Car
Satisfied Customers: 2429
Experience:  Over 30 years experience, 17 years with Audi, Factory trained
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Towing..I have all lights on trailer working except running lights

Customer Question

Towing lights, I have all lights on trailer working except running lights but the lights are working on the truck
Submitted: 7 years ago.
Category: Car
Expert:  The Audi Doctor replied 7 years ago.

Thank You for choosing Just Answer for your query. Yes, I can help you.

When you turn on the running lights does the terminal at the trailer socket receive power? If not you have a wiring problem to the trailer harness from the vehicle. Also, check the other wires. In a standard four wire system you should have left turn / left brake, right turn / right brake, tail (running), and ground .

If you have power remove a tail light and check the bulb. If the bulb is good remove it and test the socket with your test light. You should have power in the center and ground in the side of the socket. Let me know the results and I can further assist you.

I hope I have answered your questions and addressed your concerns. Should you have further questions on this matter, please do not hesitate to ask. I want you to be 100% satisfied with my answer.

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Thank You!
Customer: replied 7 years ago.
the truck lights work all phases, the trailer lights work all phases l-turn, r-turn, brakes just no running lights whats causing this
Expert:  The Audi Doctor replied 7 years ago.

Can you view my answer? I can't do a "cut and paste from my previous answer for some reason. Please let me know if you can view it and understand.


Please check this out and get back to me.


Thank You!