Where Do Vehicle and Trailer Wiring Harness Ground Wires Connect

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Question:

I keep reading that the white wire ground from the trailer wiring needs to be connected to a clean metal part of the vehicle. Then what do I connect the white wire from the vehicle side 4point wiring to?

asked by: LaRyna

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Expert Reply:

The ground wire on a trailer's wiring harness (usually a white wire) should be firmly attached to clean bare metal on the trailer frame. The white ground wire on the vehicle's wiring harness should similarly be attached to clean bare metal on the vehicle, or to an existing factory grounding point, or even directly to the battery negative terminal.

When the trailer and vehicle are connected together through their 4-pole wiring the trailer will ultimately be grounded to the vehicle battery.

Bad grounds, on either a vehicle harness or a trailer harness, can cause all sorts of weird behavior from trailer lights or even prevent an electric jack from working. You can protect ground connections from corrosion by applying dielectric grease like # 11755 to that clean bare metal surface before you connect your ground wire ring terminal. The grease blocks water and dirt from causing corrosion at that connection.

expert reply by: Adam R

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Answer 1

For your 2018 Ford F-150 you just need the Curt T-Connector Vehicle Wiring Harness #C55774. This custom harness will plug right into the round US car connector that you mentioned under your truck to provide you with a fully-functional 7-Way…

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Answer 2

The Blue Ox Patriot Braking Systems like part #BLU37TR all use a proprietary breakaway switch so you must use one from Blue Ox, the Second Vehicle Breakaway Kit for Blue Ox Patriot Supplemental Braking Systems part #BRK2505 which also comes with the…

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Answer 3

It could be a tow package fuse on the vehicle. Use the owners manual to find the locations of fuses/relays related to the tow package wiring to check them and replace as needed. If the issue is not a fuse or relay then you can test the vehicle side…

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Answer 4

You can connect the ground wire from your light to the main ground circuit on your utility trailer, but we typically recommend using a ring terminal like part #DW05702-1 and matching self-tapping screw #FA1131822 to ground it to your trailer frame as…

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Answer 5

What you will want to do is test the wires going into the box of the converter box for voltage with a circuit tester like the #3808 to see if there is voltage going into the box when the taillight functions of your vehicle are applied, and then test…

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Answer 6

I'll give you the run down on how to troubleshoot your trailer lights not functioning. The first thing to do is take a look at your owner's manual to locate any trailer fuses or relays and ensure they are all there and in working order. If…

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Answer 7

I checked with Lippert and could not find any information on NV304664. Do you know the capacity of the axle? If it is a 7,000 pound axle then the likely inner bearing is #25580 and the outer bearing is #14125A. If a 2-1/4 inch seal diameter is needed…

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Answer 8

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Answer 9

As with the installation of lights on a trailer, the lights must be grounded, either through the mounting hardware which is the case for many lights. As with trailer wiring the #RM-155 needs the bulbs to be grounded to the vehicle to complete the…

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Answer 10

In some cases trailer lighting will ground through the hitch ball but that's typically only if the actual ground circuit is insufficient. This is not an ideal setup. It needs to ground through the wiring of the trailer harness. You can test this…

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Answer 11

A hitch ball does not make a good ground connection for trailer lighting functions. The fact that the lights work for a bit after you hit a bump with the hitched trailer tells us that somewhere in your trailer and vehicle wiring there is an…

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Answer 12

If you're looking for a kit to light the side marker lights while flat towing then no, there is not currently any kits made for this purpose. The only way to get lights up front would be to use a tow bar like the Roadmaster Nighthawk All Terrain,…

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Where Do Vehicle and Trailer Wiring Harness Ground Wires Connect

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