This procedure covers the removal and replacement of the cooling fan relay in the underhood fuse/relay box on a 2021-2024 Ford F-150 with 3.5L EcoBoost engine.

Warnings

Tools required

Parts

• Cooling fan relay × 1 — Use OEM specification

Preparation

1. Park vehicle on level ground and engage parking brake
2. Allow engine to cool completely for at least 30 minutes
3. Open hood and secure with prop rod
4. Identify the underhood fuse/relay box located on the driver's side of the engine compartment near the battery

Procedure

1. 1

   Disconnect battery negative terminal
   Using a 10mm socket, loosen the nut on the negative battery terminal. Remove the cable and position it away from the battery post to prevent accidental reconnection during the repair.
2. 2

   Access the fuse/relay box
   Locate the underhood fuse/relay box on the driver's side fender well. Release the locking tabs on both sides of the cover by pressing them inward. Lift the cover up and away from the box to expose the fuses and relays.
3. 3

   Identify the cooling fan relay
   Reference the relay diagram on the underside of the fuse box cover or in the owner's manual to locate the cooling fan relay position. On the 2021-2024 F-150 3.5L EcoBoost, the cooling fan relay is typically located in position R13 or R14. Verify the relay position matches the diagram.
4. 4

   Remove the old relay
   Grasp the cooling fan relay firmly with your fingers or needle-nose pliers. Pull straight upward with steady pressure to extract the relay from its socket. Avoid twisting or rocking the relay as this may damage the socket terminals. Inspect the relay terminals and socket for any signs of corrosion, burning, or damage.
5. 5

   Install the new relay
   Inspect the new cooling fan relay to ensure the terminal configuration matches the old relay. Align the relay terminals with the socket, ensuring proper orientation by matching the relay tab or keying feature. Push the relay straight down into the socket until it is fully seated and clicks into place. Verify the relay is secure and cannot be easily pulled out.
6. 6

   Reinstall fuse box cover
   Position the fuse/relay box cover over the box, aligning the tabs on the cover with the slots on the box. Press down firmly on both sides until the locking tabs click into place and the cover is secure.
7. 7

   Reconnect battery
   Reconnect the negative battery cable to the battery post. Tighten the 10mm nut securely, ensuring good electrical contact. Do not overtighten as this may damage the battery terminal.

Reassembly

1. Ensure fuse box cover is fully seated and locked
2. Verify battery connection is tight and secure
3. Close hood when verification is complete

Verification

• Turn ignition to ON position without starting the engine and verify no warning lights appear on the instrument cluster
• Start the engine and allow it to idle
• Turn on the air conditioning to maximum and verify the cooling fans activate within 30-60 seconds
• Monitor engine temperature gauge to ensure it remains in normal operating range
• Listen for proper cooling fan operation with smooth engagement and no unusual noises
• Reinitialize power windows by holding each window switch in the down position for 2 seconds after window is fully down, then up position for 2 seconds after window is fully up

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