Where Do Vehicle and Trailer Wiring Harness Ground Wires Connect

Published 08/16/2018

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Dielectric Grease for Electrical Connectors, 2 oz.

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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

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