Replacement 7-Way and Junction Box for 5th Wheel Trailer with Non-Functioning Brakes

Updated 03/01/2018 | Published 02/28/2018

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Question:

We have run out of ideas how to get our trailer brakes to work when hauling it. I believe it’s it the fifth wheel plug since I hooked up to a friends pickup and the brakes on the trailer didn’t work. Our brakes used to work, then they worked off and on now they don’t work at all. When we try them with a manual override on the controller we get nothing. We ordered the tow package when we bought the truck. We are pulling a 2014 Cedar Creek fifth wheel trailer with a 2014 Dodge Ram 2500 diesel. Thank you! Ps the brakes on the trailer are new

asked by: Ron H

Expert Reply:

Since you have confirmed that your 5th wheel's brakes do not work even when connected to a different tow vehicle you will want to focus on the trailer for your troubleshooting. There are simple troubleshooting steps you can take to isolate the problem on the trailer.

First, I suggest checking the condition of the 7-way plug. Sometimes corrosion can develop INSIDE the plug housing where it is all but impossible to detect. Normal exposure to the elements can cause this. Since your brake issue went from an occasional problem to a permanent one, the corrosion possibility is definitely worth checking.

We offer replacement 7-way plugs like # H20046 (8-foot) and # H20044 (6-foot) but we also have a handy 7-way pre-wired to a junction box with cable, part # HS381-9000, that makes it easy to replace the whole plug and connect the trailer's wiring to the box with ring terminals # 44-5310A.

You can test your brakes independent of the 7-way plug by directly applying 12V power from your vehicle battery. Locate the main trailer ground wire and the wire for the brake circuit and connect these to the battery (you can use a set of jumper cables to make this easier). If you can hear the electric drum brakes humming that is a good sign. With this full power applied the brakes should show plenty of resistance or lock up completely.

If this test does not activate the brakes then I would suspect a wiring issue on either the main trailer ground wire or the brake circuit wire. Make sure the primary ground is firmly attached to a clean bare metal surface on the trailer. Rust, grease or other contaminants can be cleaned/sanded off to expose clean bare metal that is essential for a good ground. That restored grounding point can be protected by applying dielectric grease # 11755. If the main brake wire has cracked or worn insulation it could be shorting to the frame.