This procedure covers the removal and replacement of the horn relay located in the engine compartment fuse box of a 2015-2020 Ford F-150 with the 3.5L EcoBoost V6 engine.

Warnings

Tools required

Parts

• Horn relay × 1 — Ford FL3Z-14N089-C or equivalent

Preparation

1. Park vehicle on level ground and engage parking brake
2. Turn off ignition and remove key from vehicle
3. Open hood and secure with prop rod
4. Allow engine to cool if recently operated
5. Disconnect negative battery terminal using 10mm socket and isolate cable away from battery post

Procedure

1. 1

   Locate engine compartment fuse box
   The fuse box is located on the passenger side of the engine compartment, mounted near the firewall. It is a black rectangular box with a cover.
2. 2

   Remove fuse box cover
   Release the cover retention clips by pressing or pulling the tabs on each side of the cover. Lift the cover upward and away from the fuse box. Inspect the diagram on the underside of the cover to identify the horn relay location (typically labeled as 'Horn Relay' or with relay number).
3. 3

   Identify horn relay
   Locate the horn relay in the fuse box. It is typically a small rectangular relay with four or five pins. The relay should be clearly marked on the fuse box itself or on the cover diagram. On most F-150 models, it is positioned in the front row of relays.
4. 4

   Test relay function (optional)
   Before removal, you can test the relay by reconnecting the battery temporarily and having an assistant press the horn button while you listen for an audible click from the relay. A clicking sound indicates the relay is receiving signal but may have failed contacts. No click suggests a wiring or switch issue. Disconnect battery again before proceeding.
5. 5

   Remove horn relay
   Grasp the horn relay firmly with your fingers or use a relay puller tool. Pull the relay straight upward with steady pressure to extract it from its socket. Rock gently side-to-side if needed, but avoid bending the pins. Inspect the relay terminals and socket for corrosion, melting, or damage.
6. 6

   Inspect relay socket
   Examine the relay socket terminals for signs of corrosion, burning, or discoloration. If terminals appear damaged or corroded, clean with electrical contact cleaner and a small wire brush. Ensure socket terminals have proper tension and are not spread apart.
7. 7

   Install new horn relay
   Align the new relay with the socket, ensuring the orientation matches the diagram and that pins align with terminal slots. The relay will only fit in one orientation. Push the relay firmly and squarely into the socket until it is fully seated and flush with surrounding relays. Verify all pins are properly inserted.
8. 8

   Reinstall fuse box cover
   Position the fuse box cover over the fuse box, aligning all tabs and clips. Press down firmly on all edges until the retention clips snap into place and the cover is secure.
9. 9

   Reconnect battery
   Reconnect the negative battery terminal to the battery post. Tighten the terminal bolt to specification.
   Torque spec

   Battery Terminal Bolts6 Nm (4 lb-ft)

Reassembly

1. Ensure fuse box cover is properly secured with all clips engaged
2. Verify battery terminal is tight and secure
3. Close hood and ensure it latches properly

Verification

• Turn ignition to ON position without starting engine
• Press horn button on steering wheel and verify horn sounds properly
• Test horn several times to ensure consistent operation
• If horn still does not function, check horn fuse, wiring connections at horn, and horn button/clock spring assembly
• Verify no warning lights appear on instrument cluster related to electrical system

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