Troubleshooting Brake Controller and Not Working and the Left Tail Light No Power At 7-Way  

Question:

Expert Reply:

Since the brakes are working on the trailer when you apply power to the brake feed wire from a separate source, you have most likely eliminated the trailer wiring and brakes as the problem.

I would start out with the easiest possible solutions first and then work towards the harder to determine solutions.

Check the vehicle side trailer connector for corrosion. This can cause a short inside the connector and the brake feed circuit and ground are at the bottom of the connector so moisture affect these connections first.

Next, check the manual brake lever on the brake controller. You said that there is a small amount of current going out on the brake feed circuit. Slide the lever fully on and let it snap back several times. This will clean the contacts inside the controller and let the lever return completely to the off position.

Next, check the ground wire on the vehicle side connector and the brake controller itself. If there is a bad ground connection all sorts of different lighting problems can crop up. With the left brake light not having power also, it may be that a bad ground is causing the problem.

Finally, if none of the other suggestions have helped you will need to check the brake controller wiring and the left brake light circuit wiring. The left brake light problem may be a blown fuse in the power distribution box under the hood. The brake controller will need to be tested with a circuit tester.

Testing the brake controller requires severing the blue wire exiting the brake controller. Leave enough room to splice it back together when testing is done. Severing the blue wire eliminates any wiring problems on the brake feed circuit beyond the brake controller on the truck. If severing the blue wire and testing shows that there is no problem with the brake controller, the problem is between the controller and the trailer connector at the rear of the truck.

Here is how to test the brake controller wiring. Sever the blue brake output wire and then apply the manual slide. Using a circuit tester, item # PTW2993 if needed, you should get output to the trailer brakes. If the manual slide activates the trailer brake output wire properly, try the brake pedal. If the brake pedal activates the brake output properly also then the problem is farther back either in the vehicle wiring or on the trailer.

If either the brake pedal or the manual slide is not functioning properly you will need to test the wires going into the brake controller. Make sure you have power entering the brake controller on the black wire and on the red wire ONLY when the brake pedal is pressed.

If there is power on the red wire before the brake pedal is pressed you have connected the red wire from the brake controller to the wrong circuit. You would then need to find the brake switch wire that has power ONLY when the brake pedal is activated.

If these connections check out and the brake controller is properly grounded to the negative battery terminal then there is possibly a problem inside the brake controller.

expert reply by: Robert G

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