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Ford F-150/F-250: How to Install Trailer Wiring Harness

When you're towing a trailer, you need to make sure you have working rear lights. Learn how to install a trailer wiring harness on your Ford F-150 or Super Duty.

By Tad Brunton - October 24, 2014

This article applies to the Ford F-150 (2004-2014) and the F-250, F-350 Super Duty (2005-2014).

When you decide to tow a trailer, you need to a install a trailer wiring harness to connect your truck's brake lights to those of the trailer. Without the connection, you're at risk for an accident or traffic ticket. It is an easy installation that that shouldn't take you more than an hour to finish

Material

  • Wiring harness
  • Zip ties
  • T-connector wiring harness

Step 1 - Back your truck up to the trailer tongue

Make sure your truck is on level ground and put the truck in park. Then set the emergency brake on.

Figure 1. trailer hook up.

Step 2 – Locate the truck’s wire harness

The plug is usually located on the driver's side between the back tire and the end of the truck bed. Squeeze the center clasp and separate the two parts of the harness.

Figure 2. Wire harness under the truck bed.

Step 3 - Connect both ends of the harness

Connect both ends to the T-connector. The third end connects to your trailer's wire connection.

Figure 3. Connect both ends of the harness to your trailer's wire connection.

Step 4 - Test the lights

Ask a friend or family member to stand behind the trailer as you step on the brakes, use the turn signals, and operate your truck’s running lights.

Figure 4. Testing the lights.

Featured Video: Installation of a Trailer Wiring Harness

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