How To Troubleshoot When Your Trailer Has No Brake Or Turn Signals Functioning
Updated 11/03/2025 | Published 01/16/2025
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Question:
I have a Hopkins trailer converter. All of my lights work except my brake lights and turn signals. Could the converter possibly be bad? What could be the issue? Tail/running lights are good Brake lights are bad Turn signals are bad Every thing is good on the truck.
asked by: Jaxon H
Expert Reply:
Hey Jaxon,
It could be the converter or it could just be an issue with the wiring at the tail lights since the brake and turn signal functions run on the same wire. You'll need to use a circuit tester # PTW2993 or multimeter # PT89ZR and test for power before the converter and then after for each light signal to see if the converter is the issue.
I've attached the wiring color to function diagram for the side before the converter. After the converter the yellow will be both the left turn and stop and the green will be the right turn and stop. Brown is your running light and white is the ground. If you're not getting the signal before the converter the connection to the vehicle has an issue. If you're getting the signal through the converter and out to the trailer plug then the converter isn't the issue and would instead be somewhere on the trailer.
On the trailer you'll need to go to the tail lights and probe into the wires to test for each light function to see if it's coming through. If the signals are coming through the tail lights could just be bad or the ground might be corroded. If they aren't there's a short somewhere in the wiring running up to the connector at the tongue of the trailer.
Let me know what you find and we can keep troubleshooting.
(click to enlarge)
Product Page this Question was Asked From
Hopkins Tail Light Converter with 4-Way Flat Trailer Connector
- Custom Fit Vehicle Wiring
- Trailer Hitch Wiring
- Vehicle End Connector
- Converter
- Universal Fit
- 4 Flat
- Plug and Lead
- Splice-In
- Hopkins
more information >
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Kate F.
11/3/2025
Hey Jaxon, what did you find when you tested the wiring around your Hopkins converter? Knowing whether the power dropped before or after the converter could really help others track down similar brake and turn signal issues. Your update could make it easier for the next person with the same problem.