DodgeForum.com

Dodge Ram 1994-2008: How to Install 5th Wheel 7-Way Trailer Wire Harness

When you need to tow a 5th wheel Gooseneck trailer, you will need to install a wiring harness to connect your truck's running, brake and turn signal lights to the trailer's lighting system. Without a proper connection, you could cause an accident or be cited by law enforcement. This installation is fairly easy for 2nd and 3rd generation Dodge Rams, which is one that you can do yourself.

By August Barrett - July 20, 2015
Contributors: etrailer.com

This article applies to Dodge Ram 2nd and 3rd Generation (1994-2008).

In order to pull a 5th wheel Gooseneck trailer safely, and legally, a 90-degree 7-way wiring harness will need to be installed into the bed of your Dodge Ram. This is because the trailer harness will not reach the factory plug located on the rear of the truck, and this harness is what controls the brake lights, running lights, and turn signals. You will need to connect a 90-degree 7-way wire harness to the factory harness and plug, which will add a new outlet into the bed of your truck. As a new trailer wire harness will provide the aperture needed for the proper trailer connection, continue reading for this DIY installation guide.

Materials Needed

  • Cordless drill with hole saw
  • No. 6 self-tapping screws
  • Razor
  • 90-degree 7-way wire harness
  • Terminal grease
  • Zip ties

For this article, the Hopkins Endurance Fifth Wheel and Gooseneck 90-Degree Wiring Harness with seven-pull plug (part # HM42137) seen in Figure 1 will be installed.

Figure 1. Hopkins fifth wheel wire harness.

Step 1 – Drill into bed frame for the socket

  • Choose a location on the bed frame to install the fifth wheel wire harness socket. Also, check underneath the bed and make sure that nothing can get damaged.
  • Using a cordless drill with hole saw, drill a hole through the bed liner and frame for the socket.
  • Place the socket into the hole of the bed liner, and use a razor to cut the bed liner so the socket can have a snug fit. Do not secure the socket just yet.
Figure 2. Socket location in the truck bed.

Pro Tip

Choose the socket location wisely. You do not want to install the new plug and socket in an area where the wire harness might get fouled or cause other problems.

Step 2 – Install the fifth wheel socket

  • Feed the single-plug end of the wire harness underneath the truck bed and through the hole socket hole.
  • Apply terminal grease to the 7-way plug and connect it to the socket. Make sure you hear them lock together.
  • Position the socket onto the frame and secure it using four self-tapping screws.
  • Figure 3. Feed the wire harness from under the truck bed.
  • Figure 4. Secure socket to the truck's bed wall.

Step 3 – Ground and route the wire harness

  • Route the other end of the wire harness (with two plugs) over the frame rail at rear end of the truck to hold up the wire harness.
  • Then use a self-tapping screw to secure the white wire ring terminal to a metal part of the frame.
  • Secure the excess wiring with zip ties.
  • Figure 5. White ground wire secured to metal frame.
  • Figure 6. Zip tie excess wiring.

Step 4 – Connect the new wire harness

  • Disconnect the factory wire harness from the factory plug located on the inside of the bumper. Push the red tab down as you pull the wire harness away from the plug in the bumper.
  • Apply terminal grease to the factory harness.
  • Then connect the factory harness to one of the new wire harness. Make sure that you push the red tab and hear it click to secure the connection.
  • Add terminal grease to the other plug of the new wire harness.
  • Connect the new wire harness to the factory plug in the bumper. Again, make sure the red tab is pushed in.
  • Zip tie any excess wiring.
  • Figure 7. Pull back red tab to remove the factory harness.
  • Figure 8. Press red tab to lock the old harness to the new harness.

Related Discussions and Video