Main Relay

Replace the main relay (horn relay) on a 1966 Chevrolet Corvette, which controls the horn circuit and is located in the engine compartment fuse panel area.

Warnings

Tools required

Parts

• Main relay (horn relay) × 1 — Delco-Remy D-1604 or equivalent 12V automotive relay
• Dielectric grease × 1 — Small packet for electrical connections

Preparation

1. Park vehicle on level surface and engage parking brake
2. Turn ignition to OFF position and remove key
3. Disconnect negative battery cable using 1/2" wrench or socket
4. Allow engine to cool if recently operated
5. Locate the relay panel on the driver side firewall near the fender well

Procedure

1. 1

   Access the relay panel
   Remove the access cover over the relay/fuse panel if equipped. On 1966 Corvettes, the horn relay is mounted directly in the engine compartment (commonly on the firewall) and is generally not behind a dedicated access cover; locate it visually rather than removing a panel. Remove the screws and set the cover aside.
2. 2

   Identify the main relay
   Locate the main relay (horn relay) in the relay panel. It is typically a cylindrical or rectangular metal canister with 3-4 terminals on the base. The relay is an engine-compartment-mounted canister. Refer to a 1966 Corvette factory wiring diagram or assembly manual to confirm identification.
3. 3

   Document wire connections
   Before disconnecting, note the wire color and terminal position for each connection on the relay. The typical configuration includes: battery feed (red wire), horn button/switch input (white or green wire), ground (black wire), and horn output (varies). Mark wires with tape or take a photo for reference, and verify actual terminal functions against the 1966 Corvette factory wiring diagram rather than assuming wire colors.
4. 4

   Test existing relay function
   Reconnect battery temporarily. Use a test light to verify power at the battery feed terminal with ignition off. Disconnect battery again after testing. This confirms the circuit has power and helps diagnose if the relay is actually faulty.
5. 5

   Disconnect relay wiring
   Remove each wire terminal from the relay base. Most 1966 Corvette relays use push-on spade terminals that can be pulled straight off. If terminals are corroded, gently wiggle while pulling. Use needle-nose pliers if necessary, gripping the terminal connector body, not the wire.
6. 6

   Remove old relay from mounting
   The relay is held by a mounting bracket secured with a single screw or bolt through the relay mounting tab; verify exact fastener size against the factory assembly manual. Remove this fastener and extract the relay from the panel. Note the orientation of the mounting tab for proper reinstallation.
7. 7

   Clean terminal connections
   Inspect all wire terminals for corrosion or damage. Clean terminals with a wire brush and electrical contact cleaner. Replace any terminals that are cracked, burned, or have compromised spring tension. Ensure all terminals will make firm contact with the new relay.
8. 8

   Install new relay
   Position the new relay in the mounting bracket with the terminal orientation matching the old relay configuration. Secure with the mounting screw, tightening firmly but not overtightening to avoid cracking the relay base or bracket.
9. 9

   Reconnect wiring
   Reconnect each wire terminal to the corresponding relay terminal post according to your documentation from Step 3. Push each terminal fully onto the post until it clicks or seats completely. Apply a small amount of dielectric grease to each connection to prevent corrosion.
10. 10

    Reinstall access cover
    Replace the relay panel access cover and secure with the 2 mounting screws. Ensure the cover is properly seated and not pinching any wires.

Reassembly

1. Reconnect battery negative terminal and tighten securely
2. Verify no tools or parts are left in engine compartment

Verification

• Turn ignition to ON position without starting engine
• Press horn button and verify horn sounds clearly and immediately releases when button is released
• Check for any burning smell or excessive heat from the relay during horn operation
• Verify all other electrical systems function normally (headlights, wipers, gauges)
• Test horn function multiple times with varying button press durations to ensure relay cycles properly

More procedures for this vehicle