Horn Relay

This procedure covers the removal and replacement of the horn relay in a 2022 Rivian EDV 500 electric delivery van, requiring access to the main power distribution module.

Warnings

Tools required

Parts

• Horn relay × 1 — Use OEM specification
• Dielectric grease × 1 — Small packet

Preparation

1. Park vehicle on level surface and engage parking brake
2. Ensure vehicle is powered off and key fob is at least 20 feet away from vehicle
3. Open the front hood and secure with prop rod
4. Locate the 12V auxiliary battery in the front compartment (driver side)
5. Disconnect negative terminal of 12V battery and wait 5 minutes
6. Disconnect positive terminal of 12V battery and isolate both cables

Procedure

1. 1

   Remove lower dashboard access panel
   From inside the driver's side cabin, locate the lower dashboard panel beneath the steering column. Use trim removal tools to carefully release the retaining clips starting from the bottom edge. Remove the panel and set aside. Disconnect any electrical connectors for diagnostic port or lights if equipped.
2. 2

   Access the central power distribution module
   Behind the lower dashboard panel, locate the central power distribution module (PDM). This is a black rectangular box approximately 8x6 inches mounted to the left side of the steering column support. Remove the two Torx T25 screws securing the PDM cover.
3. 3

   Remove PDM cover and identify horn relay
   Carefully remove the PDM cover. Inside, locate the horn relay using the legend printed on the underside of the cover or on the PDM itself. The horn relay is typically labeled 'HORN' and is positioned in the second row, third position from left. Take a photo for reference before proceeding.
4. 4

   Test horn relay for fault confirmation
   Using a digital multimeter, test the relay coil resistance between terminals 85 and 86. Should read approximately 70-90 ohms. Test continuity between terminals 30 and 87a with relay at rest (should show continuity). If relay is faulty, readings will be out of specification or show no continuity.
5. 5

   Remove failed horn relay
   Grasp the horn relay firmly and pull straight up with steady pressure to release it from the socket. Do not twist or rock the relay as this may damage the socket pins. Inspect the socket for any signs of corrosion, burning, or damage. If socket shows damage, note this for additional repair.
6. 6

   Inspect relay socket and clean if necessary
   Examine the relay socket terminals for any corrosion, discoloration, or bent pins. If corrosion is present, use electrical contact cleaner and a small brush to clean the terminals. Ensure all pins are straight and properly aligned. Allow to dry completely before proceeding.
7. 7

   Apply dielectric grease to new relay
   Apply a thin coat of dielectric grease to the metal blade terminals of the new horn relay. This prevents corrosion and ensures good electrical contact. Do not apply grease to the plastic body or inside the socket.
8. 8

   Install new horn relay
   Align the new horn relay with the socket, ensuring the relay orientation matches the diagram on the PDM or cover. The relay will only fit one way. Push firmly and evenly until the relay is fully seated and flush with adjacent relays. Verify it is secure by gently attempting to pull it back out.
9. 9

   Reinstall PDM cover
   Position the PDM cover back onto the module housing, ensuring all edges are aligned. Install the two Torx T25 screws and tighten securely by hand. Do not overtighten as the mounting points are plastic.
10. 10

    Reconnect 12V battery
    Return to the front hood area. First reconnect the positive terminal of the 12V battery and tighten securely. Then reconnect the negative terminal and tighten securely. Ensure connections are clean and tight.
11. 11

    Perform initial system check
    With the 12V battery reconnected, bring the key fob near the vehicle. The vehicle should wake and initialize systems. Wait for all dashboard warnings to clear (approximately 2-3 minutes). Do not proceed to testing until initialization is complete.
12. 12

    Test horn operation
    Sit in the driver's seat and press the horn button on the steering wheel. The horn should sound immediately and continuously while pressed. Test multiple times with varying press durations. Also test the panic button on the key fob to ensure horn functions with that input as well.

Reassembly

1. Reinstall the lower dashboard access panel by aligning the clips and pressing firmly until all clips engage
2. Reconnect any electrical connectors that were disconnected from the dashboard panel
3. Verify all trim panels are securely fastened with no gaps or loose clips
4. Secure any loose wiring with cable ties if needed
5. Close and secure the front hood

Verification

• Test horn by pressing steering wheel horn button - should sound immediately with clear, loud tone
• Test horn duration - should sound continuously as long as button is pressed
• Test panic alarm on key fob - horn should chirp repeatedly
• Verify no warning lights remain on dashboard related to horn or electrical system
• Check that all other electrical accessories function normally (lights, wipers, HVAC)
• Perform a test drive to ensure no other systems were affected by the repair

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