why do my Ford F-150 tail lights not work when the headlights are on?

Ford F-150 12th Generation (2009-2014)

Error Codes

1-2 hours

Time

medium

Difficulty

medium

Severity

3 min read

566 words

Problem Statement

Learn how to diagnose and fix tail lights not working when headlights are on in Ford F-150. Step-by-step guide with diagnostic procedures and repair instructions.

Affected Component

Electrical

Estimated Time

1-2 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical components.
•Allow the vehicle to cool down before inspecting any components if recently driven.

Symptoms

•Tail lights do not illuminate when headlights are on
•Brake lights may still function correctly
•Check engine or warning lights on the dashboard may illuminate
•No blown fuses in the tail light circuit
•Dim or flickering tail lights when headlights are turned on

Diagnostic Steps

1
Inspect the tail light bulbs for any signs of damage or burnout.
2
Check the fuse box for any blown fuses related to the tail lights or exterior lighting.
3
Use an OBD-II scanner to check for any diagnostic trouble codes that may indicate underlying electrical issues.
4
Test the tail light circuit for voltage using a multimeter with headlights on.
5
Examine the wiring and connectors for corrosion, damage, or loose connections.
6
Verify the operation of the light switch by checking for continuity with a multimeter.

Solution

💡 Expert Tip

For complex repairs like this, consider taking photos at each step. This helps if you need to reverse a step or consult with a mechanic. Also, keep all removed parts organized - you may need to reference them during reassembly.

Verification

After completing the repair, verify that the issue has been resolved:

✓Test the affected component to ensure it functions correctly
✓Check for any error codes or warning lights
✓Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

•Follow the manufacturer's recommended maintenance schedule
•Address warning signs early before they develop into major issues
•Use quality parts and fluids recommended for your vehicle
•Keep detailed records of all repairs and maintenance

Tools & Equipment Required

•Socket set
•Multimeter
•Fuse puller
•Electrical contact cleaner

Parts Required

•Tail light bulbs (as needed)
•Fuses (as needed)

Related Faults

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Diagnostic Steps

1
Inspect the tail light bulbs for any signs of damage or burnout.
2
Check the fuse box for any blown fuses related to the tail lights or exterior lighting.
3
Use an OBD-II scanner to check for any diagnostic trouble codes that may indicate underlying electrical issues.
4
Test the tail light circuit for voltage using a multimeter with headlights on.
5
Examine the wiring and connectors for corrosion, damage, or loose connections.
6
Verify the operation of the light switch by checking for continuity with a multimeter.

Solution

1. Preparation

Gather necessary tools and parts.
Ensure the vehicle is parked on a flat surface and the ignition is off.
Disconnect the battery to prevent electrical shock.

2. Remove Tail Light Assembly

Use a socket set to remove the screws or bolts securing the tail light assembly.
Carefully pull the tail light assembly out to access the bulbs and wiring.
Disconnect the wiring harness from the tail light assembly.

3. Inspect and Replace Bulbs

Remove the tail light bulbs from the socket and inspect for any damage.
Replace any burnt-out bulbs with new ones of the same type (check the owner's manual for specifications).

4. Check and Replace Fuses

Locate the fuse box and identify the fuse related to the tail lights.
Remove the fuse using a fuse puller and inspect it for continuity; replace if blown.
Ensure the new fuse matches the amperage rating specified on the fuse box cover.

5. Repair Wiring Connections

Inspect the wiring harness for any signs of wear, fraying, or corrosion.
Repair any damaged wires using electrical tape or replace sections of the wire if necessary.
Clean any corroded connectors with electrical contact cleaner and reconnect securely.

6. Reassemble and Test

Reconnect the wiring harness to the tail light assembly.
Secure the tail light assembly back into place with screws or bolts.
Reconnect the battery and test the tail lights by turning on the headlights.