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Troubleshooting Trailer Brakes Not Working After Installing New Controller and Wiring  

Question:

We have rewired the truck to the trailer. All brake lights blinkers Work fine. But we have no breaks on the trailer. Have replaced Controller and Controller and the Trailer plug in outlet. But still have no trailer breaks can you please help thank you

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Expert Reply:

I would be happy to help!

First, we need to see exactly where the signal of the trailer brakes is getting lost. Using a circuit tester like # PTW2993 check the 5 o'clock pin on your 7-way connector while the vehicle is on and while a buddy is engaging the manual override on the controller.

If you are getting power, then that means the issue is on the trailer side. You will need to make sure the brake output wire is installed in the correct pin of your trailers connector as shown in the included diagram.

Next trace the wires from the connector to the brake assemblies looking for any damage to the wiring that will need to be replaced. Make sure the connections to the brake magnets are secure, and one wire on the brake magnet is grounded to the frame of the trailer. If your trailer is aluminum or has a tilt bed you may need to run jumper wires from the ground wire to the main ground on the tongue of the trailer.

Now if you did not have power in the 7-way on your vehicle the issue is on the vehicle side. Cut the blue wire on the back of the controller at least 6" from the back of the controller and using the circuit tester check for power on the short wire when applying the manual override.

If you have power the issue is in the wiring between the controller and 7-way connector. You will need to trace the wire to the 7-way looking for any damage, or use # 10-1-1 to run from the controller to the 7-way to bypass the original wiring.

Lastly if you do not have power at the controller, I recommend double checking that the controller was wired correctly. On the controller you have 4 wires that have the following functions:

Black wire is 12v power, needs to go to positive terminal of battery with 20- or 30-amp circuit breaker as listed in instruction manual
White wire is ground
Blue wire is brake output wire that goes to 7-way connector
Red wire is the brake signal wire that gets installed to the cold side wire of stop light switch that only has power when the brake pedal is pressed.

I went ahead and included a link to a helpful article on wiring for you to take a look at.

expert reply by:
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Samuel C
7-Way Connector Wiring Diagram
7-Way Connector Wiring Diagram
(click to enlarge)

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