Troubleshooting 7-Way RV Wiring for Cause of Smoke from Connectors

Updated 01/21/2019 | Published 01/18/2019

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Question:

When we connect the plug from the Rv to the truck It smokes Husband said it has a good ground.

asked by: Heidi B

Expert Reply:

If your 7-way connectors are getting hot enough to smoke then you do definitely have a good ground! Without a good ground not enough power would be passed to heat up your wiring connectors and make them smoke. But clearly there is a circuit problem in either or both the vehicle socket or the RV plug.

Since it sounds like the truck's socket does not act up by itself, only when the trailer is plugged in, I suspect the issue to be on the trailer, specifically within its 7-way molded plug. I linked a photo of a 7-way trailer-side plug to show which pins carry which circuit functions.

What can happen is that moisture can migrate into the inside of the plug where it can cause corrosion. This corrosion can cause two adjacent circuits to become bridged together. If the 12V auxiliary power circuit were shorted then this could very easily cause the heat and smoke.

The easiest way to replace a trailer 7-way is using a junction box like # HS381-9000. This includes a new 7-way and inside the box are terminals to allow you to attach the existing trailer wires. You will need ring terminals # 44-5310A for the larger 10- and 12-gauge wires and ring terminals # DW05702-1 for the smaller 14- and 16-gauge wires.

You can test your truck 7-way easily using a simple circuit tester like # PTW2992 while a helper activates each of the circuits, one at a time while you apply the tester to the appropriate contact.