This procedure covers the diagnosis, removal, and replacement of a generic electrical relay on a 1966 Chevrolet Corvette with the 327ci V8 engine.

Warnings

Tools required

Parts

• Replacement relay × 1 — Use OEM specification matching original relay amperage and terminal configuration
• Dielectric grease × 1 — Generic automotive dielectric grease

Preparation

1. Park the vehicle on level ground and set the parking brake.
2. Turn off all electrical accessories and remove the ignition key.
3. Disconnect the negative battery cable (or positive cable if your vehicle has a positive-ground system).
4. Locate the relay that requires replacement. Common relay locations include the fuse panel under the dashboard, the firewall, or near the component they control.
5. Identify the relay function if not already known by consulting the wiring diagram or tracing the circuit.

Procedure

1. 1

   Test the suspected relay
   Before removing the relay, use a digital multimeter to verify the relay is faulty. Set the multimeter to continuity or resistance mode. Test for continuity across the relay coil terminals. You should read the coil resistance, usually between 50-200 ohms. If the reading is infinite or zero, the relay coil is faulty. Next, check for continuity between the common and normally-open terminals (typically terminals 30 and 87) with the relay de-energized; there should be no continuity. If there is continuity when the relay is not energized, the contacts are stuck closed.
2. 2

   Document the relay wiring configuration
   Before disconnecting any wires, note the wire colors and their terminal positions on the relay. The 1966 Corvette uses a mix of blade-type and stud-mount relays depending on application. Take a photograph or make a detailed sketch showing which wire connects to which terminal. Original 1966 relays predate the modern ISO terminal numbering (85/86/30/87/87a) convention and use GM-specific terminal markings; rely on your own documented wire colors and positions rather than assuming standard numbers.
3. 3

   Disconnect the relay wiring
   Carefully disconnect each wire from the relay terminals. For blade-type connectors, gently pull the connector straight off the blade terminal. For stud-mount relays with ring terminals, use a screwdriver or wrench to remove the retaining nuts. Keep track of any washers or insulating sleeves. If wires are corroded or stuck, gently wiggle while pulling to avoid damaging the wire insulation.
4. 4

   Remove the relay mounting hardware
   Remove the relay from its mounting bracket. Most 1966 Corvette relays are secured with a single mounting screw or clip. For screw-mounted relays, remove the mounting screw completely. For clip-mounted relays, squeeze the retaining clips or tabs and pull the relay free from the mounting bracket. On this era of vehicle, relays are typically discrete units mounted to the firewall, fender, or near the component they control, rather than plug-in socketed types.
5. 5

   Inspect the relay mounting location and terminals
   Examine the mounting bracket, socket, or terminal area for signs of heat damage, corrosion, or melted wiring. Clean any corrosion from the terminals or mounting hardware using a wire brush or electrical contact cleaner. Check that the mounting bracket is secure and not damaged. Heat discoloration around terminals indicates a poor connection that should be addressed by cleaning or replacing damaged connectors.
6. 6

   Verify replacement relay specifications
   Compare the original relay to the replacement. Verify that the terminal configuration matches exactly, including terminal spacing and orientation. Check that the voltage rating matches the vehicle's 12-volt system. Confirm the amperage rating is equal to or greater than the original relay. The relay coil resistance should be similar to the original. Match the replacement relay's voltage and amperage rating to the original relay for that specific circuit.
7. 7

   Install the new relay
   Position the new relay in the mounting bracket or socket, ensuring it is oriented correctly according to your documentation from Step 2. Secure the relay with the mounting screw or push firmly into the clip until it clicks into place. For screw-mounted relays, hand-tighten the mounting screw snugly but do not overtighten, as this can crack the relay housing.
8. 8

   Reconnect the relay wiring
   Reconnect each wire to its corresponding terminal on the new relay according to your documentation. Ensure each connector is fully seated on blade terminals with a firm click or snap. For stud-mount terminals, place ring terminals over the studs in the correct order, add any washers or insulating sleeves, and thread on the retaining nuts. Tighten stud nuts firmly but do not overtighten. Apply a small amount of dielectric grease to each connection to prevent future corrosion.
9. 9

   Verify installation and test the circuit
   Double-check that all connections are secure and properly oriented. Reconnect the battery cable. Turn the ignition to the ON position (do not start the engine yet). Activate the circuit controlled by the relay (headlights, horn, etc.) and verify proper operation. Listen for the relay clicking when activated, indicating the coil is energizing and contacts are closing. Use a multimeter to verify voltage at the relay output terminal when activated. If the circuit does not function properly, recheck all connections and relay orientation.

Reassembly

1. Ensure all wire connections are clean, tight, and protected with dielectric grease.
2. Verify the relay is securely mounted and all mounting hardware is tightened.
3. Route any displaced wiring back to its original path, securing with clips if necessary.

Verification

• With the battery reconnected and ignition ON, activate the relay-controlled circuit multiple times to verify consistent operation.
• Listen for a clear, distinct click from the relay each time it activates, indicating proper coil and contact function.
• Check that the controlled component (lights, fuel pump, etc.) operates at full power without flickering or intermittent operation.
• Verify no smoke, unusual odors, or heat buildup occurs at the relay or connections during operation.
• If possible, measure voltage drop across the relay contacts under load; it should be less than 0.5 volts, indicating good contact integrity.

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