How to Check Electric Brakes and Wiring on a 36 Foot Gooseneck Trialer with Brakes on Two Axles

Question

Question:

I have a 36 goosneck trailer that I just bought. Im having a heck of a time getting the brakes to work properly. Ive replaced the brakes with new dexters, new break away switch, battery and lead that plugs into truck. I have not yet replaced the brake wire that runs back to the brakes2 strand. I did notice that when I trimmed it back to get new wire it was blackish in color. Im getting 11.85 volts at the plug on the truck and to the junction box. On the last brake on the trailer Im only getting like 8.45 volts. I can feel them grabbing, but barely stopping the truck. Do you have any sugestions because I need brakes since we will be moving the house. Do the brake magnets matter which lead is connected to the positive or negative since they are not marked and just white wires? Everything else works fine just the brakes electric only. The controller works well on my camper. Any really good diagrams of how the junction box should be, or should I try re-wiring the brakes complete ly? Thanks

asked by: Brian

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Expert Reply:

It sounds like you had a short on the electric brake controller wiring at some point, since the wires are black. This indicates the wiring was overheated. The first thing I would do is check the 7-Way connector on the trailer and the truck for proper wiring. I attached a link to our wiring page for you. This page shows the correct placement of wires inside the vehicle and trailer side 7-Way connectors about 1/2 way down the page.

Once you are sure the vehicle and trailer connectors are wired properly, you will need to make sure that the electric brake power and ground wire going into the junction box are connected correctly to the power and ground wire coming out of the junction box and going to the electric brakes. The power and ground wires running to the brake magnets can be attached to either wire coming out of the magnet, the magnet will work either way.

Since you said that you replaced the brakes with new Dexter brakes, I am assuming you mean you replaced the complete brake assembly. If this is the case the magnets should be fine. If you did not replace the magnets you should check them to be sure that one or more of them are not shorted. We have an article, see link, that details how to test each magnet. Sever the wires at each magnet and follow the direction for testing individual brake magnets. You can also test the brake magnet resistance to verify if the magnets are good or not.

Whether the the magnets are good or not, I would recommend replacing the wire from the junction box back to all brake magnets with an appropriate length of double bonded wire, # 10-2-1.

Finally, electric trailer brakes are not designed to stop the truck and trailer without the use of the truck brakes, they are designed to assist the truck in stopping the loaded weight of the trailer. You will always get a slightly lower reading at the magnets that are wired farthest from the brake controller output, but you should still get more than the amount you are describing. You might want to go back to your brake controller instructions and setup the brake controller again, with the gooseneck trailer attached. It may be that you are still setup for your camper trailer, or that you have missed a step.

Let me know what you come up with and if this does not help, we will look into some other testing that we can do to see if the brake controller is functioning properly. I will need to know the brand and model of the brake controller you have installed as well as the year-make-model of your tow vehicle.

expert reply by: Robert G

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How to Check Electric Brakes and Wiring on a 36 Foot Gooseneck Trialer with Brakes on Two Axles

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