This procedure covers the removal and replacement of a generic relay in the 2015-2020 Ford F-150 with 3.5L EcoBoost engine, typically located in the underhood or interior fuse/relay box.

Warnings

Tools required

Parts

• Relay (specific to circuit being replaced) × 1 — Use OEM specification - varies by relay function

Preparation

1. Park vehicle on level surface and engage parking brake
2. Turn ignition off and remove key from vehicle
3. If replacing a high-current relay (fuel pump, cooling fan, starter), disconnect negative battery terminal
4. Locate the appropriate fuse/relay box - underhood box is on passenger side firewall, interior box is below left side of instrument panel
5. Identify the specific relay to be replaced using the diagram on the fuse box cover or owner's manual

Procedure

1. 1

   Access the relay box
   For underhood relays: Release the fuse box cover tabs and remove the cover. For interior relays: Pull down the fuse panel door below the instrument panel on the driver's side. Note the relay location diagram on the cover for reference.
2. 2

   Identify the target relay
   Cross-reference the relay location diagram with the specific relay you need to replace. Common relays include fuel pump relay, cooling fan relay, starter relay, and horn relay. Verify the relay number matches the circuit experiencing issues.
3. 3

   Remove the faulty relay
   Using a relay puller tool or needle-nose pliers, grip the relay body firmly and pull straight upward with steady pressure. Do not twist or rock the relay excessively as this can damage the socket terminals. If resistance is encountered, gently wiggle side-to-side while pulling upward.
4. 4

   Inspect the relay socket
   Examine the relay socket terminals for corrosion, heat damage, or deformation. Look for discoloration indicating overheating. If terminals appear corroded, spray with electrical contact cleaner and allow to dry. If terminals are damaged or melted, the entire fuse box may require replacement.
   ⚠Evidence of melted terminals or heat damage indicates an underlying electrical problem. Do not simply replace the relay without diagnosing the root cause of excessive current draw.
5. 5

   Verify new relay specifications
   Confirm the replacement relay matches the original in amperage rating, voltage, and terminal configuration. The relay should have the same number of terminals (typically 4 or 5) and matching part number or Ford specification. Using an incorrect relay can result in circuit malfunction or fire.
6. 6

   Install the new relay
   Align the new relay with the socket, ensuring the terminal pins match the socket configuration. Some relays are keyed and will only fit one way. Press the relay firmly into the socket until it is fully seated and flush with surrounding relays. You should feel it click into place.
7. 7

   Reinstall fuse box cover
   Position the fuse box cover and ensure all tabs are properly aligned. Press the cover firmly until all clips engage. For interior panels, ensure the door closes securely. Verify the relay location diagram is visible for future reference.
8. 8

   Reconnect battery if disconnected
   If the negative battery terminal was removed, clean both the terminal and battery post with a wire brush. Reconnect the negative cable and tighten to specification. After reconnection, the vehicle may require relearning procedures for windows, radio presets, and other electronic systems.
   Torque spec

   Battery Terminal Bolts6 Nm (4 lb-ft)

Reassembly

1. Ensure all fuse box covers are properly secured and latched
2. Verify no tools or parts were left in the engine compartment or interior

Verification

• Turn the ignition to ON position (engine off) and verify the malfunction indicator lamp or warning light associated with the relay circuit has cleared
• Start the engine and verify the system controlled by the relay operates correctly (fuel pump primes, cooling fans activate when hot, horn sounds, etc.)
• Check for any new warning messages on the instrument cluster
• If the problem persists after relay replacement, further electrical diagnosis of the circuit and load component is required

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