7-way plug also known as the Airstream trailer plug

Is that fat black cable that connects your Airstream to your tow vehicle a mystery to you? 

While it might seem like a simple plug, it's actually one of the most important things on your Airstream—because without it functioning properly, you aren't going anywhere!

It's known by a few names:

  • the trailer plug
  • 7-way connector
  • umbilical cable

You want to keep this plug happy—which means clean, dry, and free of corrosion—so that it doesn't act up and put an end to your travels.

This plug does several important things:

  1. It connects the trailer's turn signals, brake lights, and running lights to the tow vehicle. When the truck signals, stops, or has lights on, so will the trailer.
  2. It activates the brakes on the trailer. This is probably the most important thing. Without a good connection at the plug, your trailer might not have reliable brakes. Without the brakes functioning properly, the trailer is likely to push the tow vehicle out of control during a stop or turn.
  3. It activates the backup camera. The factory-installed backup camera is powered only when the license plate light is on, and the license plate light only goes on when you turn on the lights in your truck.
  4. It provides a small amount of power to keep the trailer's batteries charged during towing.

Why is it called a "7-way" plug?

Since 1989 all Airstreams have used the same wiring arrangement. (Older trailers may have had different wiring, but usually they have been rewired to fit modern tow vehicles.)

Each location in the 7-way plug is dedicated to a specific signal. Two of them—the 12 volt positive and 12 volt negative—supply power to keep the battery charged while towing to prevent depleting the battery while using the electric brakes.

The other pins carry signals to activate the clearance lights, turn signals, brake lights, and even backup lights (but most Airstream trailers don't have those).

Keeping the plug clean is important

Over time, corrosion will happen on the seven brass connectors inside the plug. You should strive to keep the brass looking shiny yellow (not dark brown or black) so that electrical signals aren't impeded. It’s difficult to clean those connectors without the right tools, so we include the burnishing tool and products you need to do it, in our Maintenance Essentials Kit

You can also use the same tool to clean the connectors in the truck's 7-way outlet, if they need a little help. Plan to do this simple cleaning job at least once a year as preventative maintenance. With the right tools it takes just a few minutes.

Is your cable the right length?

Take a look at the 7-way cable the next time your Airstream is hitched up. Does it drag on or very near the ground? It will wear away quickly if it touches the ground during ordinary towing.

If the cord droops to touch the ground briefly in a sharp turn, that's okay. But if it's touching the ground all the time, you can wrap excess cord around the hitch post or re-route the cord in another way to take up some of the slack.

Ensure that the cable has enough slack so that the tow vehicle can make very sharp right and left turns in a parking lot without pulling the cable taut. If your cable is too short, you can buy an extension cable or (better) have the entire cable replaced. On vintage Airstreams, old stiff cables are common, so replacement is a good idea anyway.

When hitching up…

…double-check that the plug is inserted fully each time. Often it feels like it is in all the way when it really isn’t. To be sure, kneel down and look at the connection from the side. There are little tabs on the plug and the lid of the receptacle on the tow vehicle, which lock the plug into place.

If the plug isn’t inserted fully, you’ll be able to see it from the side much more easily than from the rear, and this will ensure it doesn’t come loose while towing and leave you without brakes.

Between trips, protect the plug

Be sure to position the plug between trips so that the head of plug is hanging downward. That will help keep rainwater from settling in the plug. At various RV stores and on Amazon you can find a generic “7-way plug holder” that mounts to the A-frame, which gives you a place to lock the plug and keep it out of the weather when it’s not in use.

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