Horn Relay

This procedure covers the replacement of the horn relay in a 2015-2020 Ford F-150 with 5.0L V8 engine, located in the engine compartment fuse box.

Warnings

Tools required

Parts

• Horn relay × 1 — Ford Part# CJ5Z-14N089-A or equivalent mini relay

Preparation

1. Park vehicle on level surface and engage parking brake
2. Turn ignition off and remove key
3. Allow engine to cool if recently operated
4. Locate the engine compartment fuse/relay box on the passenger side firewall near the battery

Procedure

1. 1

   Disconnect battery negative terminal
   Using a 10mm socket, loosen the negative battery terminal bolt and disconnect the cable. Move the cable away from the battery post to prevent accidental reconnection during the repair.
   Torque spec

   Battery Terminal Bolts6 Nm (4 lb-ft)
2. 2

   Open fuse box cover
   Release the tabs on the engine compartment fuse box cover and remove it. Set the cover aside in a clean location. The fuse and relay diagram is typically printed on the underside of the cover.
3. 3

   Identify horn relay location
   Locate the horn relay using the diagram on the fuse box cover. In most 2015-2020 F-150 models, the horn relay is labeled on the diagram and is a mini relay (smaller than the standard relays). It may be labeled as 'HORN' or with a relay number in the 30-40 range.
4. 4

   Remove old horn relay
   Firmly grasp the horn relay with needle-nose pliers or a relay puller tool and pull straight up with steady pressure. The relay should release from its socket. Avoid rocking the relay side-to-side as this can damage the socket terminals.
5. 5

   Inspect relay socket
   Examine the relay socket for any signs of corrosion, heat damage, or bent terminals. If corrosion is present, spray electrical contact cleaner into the socket and allow to dry completely. If terminals are damaged or melted, the entire fuse box may require replacement.
6. 6

   Install new horn relay
   Align the new horn relay with the socket, ensuring the orientation matches the diagram (relays have a specific orientation with the tabs matching socket guides). Press firmly and evenly until the relay is fully seated and flush with surrounding relays. You should feel a positive click when properly installed.
7. 7

   Reinstall fuse box cover
   Position the fuse box cover over the fuse box and press down firmly on all edges until all tabs click into place. Ensure the cover is fully sealed to prevent moisture ingress.
8. 8

   Reconnect battery negative terminal
   Reconnect the negative battery cable to the negative battery post. Tighten the terminal bolt to specification using a torque wrench. Ensure the connection is secure but do not overtighten as this can damage the battery post or terminal.
   ⚠Do not overtighten battery terminal as specified - overtightening can crack the battery post or strip the terminal threads.
   Torque spec

   Battery Terminal Bolts6 Nm (4 lb-ft)

Reassembly

1. Ensure fuse box cover is properly secured with all tabs engaged
2. Verify battery terminal is tight and has no movement

Verification

• Turn ignition to ON position (engine off) and press the horn button on the steering wheel - horn should sound continuously while button is pressed
• Test horn multiple times with short presses to verify consistent operation
• If horn does not work, verify correct relay location was used and that relay is fully seated in socket
• Check for any blown fuses related to the horn circuit if horn still does not function
• Reset power windows and other electronics as needed per owner's manual procedures

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