Cooling Fan Relay

Replacement of the cooling fan relay on a 1966 Chevrolet Corvette 327ci V8, including removal of old relay and installation of new relay.

Warnings

Tools required

Parts

• Cooling fan relay × 1 — Use OEM specification or equivalent 12V 30A automotive relay
• Dielectric grease × 1 — Small packet

Preparation

1. Park vehicle on level ground and apply parking brake
2. Turn ignition off and remove key
3. Disconnect negative battery terminal and secure cable away from battery post
4. Allow engine to cool completely if recently operated
5. Locate the relay panel or fuse box - typically mounted on the firewall or inner fender well on driver's side

Procedure

1. 1

   Access relay mounting location
   Open the hood and secure it in the raised position. Locate the cooling fan relay on the firewall or inner fender well. On 1966 Corvettes with aftermarket electric fans, the relay is typically mounted near the fan motor or on the radiator support. If a relay panel is present, identify the cooling fan relay by tracing wires from the fan motor or consulting any labeling on the panel.
2. 2

   Inspect and document wiring connections
   Before removing the relay, note or photograph the wire connection positions. The relay typically has 4 terminals: two for the coil (control circuit from temperature switch) and two for the power circuit (from battery to fan motor). Tag wires if necessary using masking tape and marker to ensure correct reassembly.
3. 3

   Test existing relay (optional)
   If troubleshooting, use a multimeter to test relay function. Check for 12V power at the battery feed terminal with ignition on. Check for ground signal from the temperature switch terminal when engine is hot. Test relay coil resistance between control terminals and compare against the specific relay manufacturer's specification (a typical 12V automotive relay coil reads roughly 60-120 ohms). This helps confirm the relay is the faulty component.
4. 4

   Disconnect relay wiring
   Remove the electrical connectors from the relay terminals. If the relay uses spade terminals, gently pull each connector straight off using needle-nose pliers if needed. If the relay is plug-in style with a socket, release any locking tab and pull the relay straight out from the socket.
5. 5

   Remove relay from mounting bracket
   If the relay is secured with a mounting bracket or clip, use a flathead screwdriver to release the retaining clip or remove the mounting screw. Lift the old relay out of its mounting location. If the relay is mounted in a socket, it may simply pull straight out without additional fasteners.
6. 6

   Clean electrical connections
   Inspect all wire terminals and relay socket for corrosion, dirt, or damage. Use a wire brush to clean corroded terminals. Spray electrical contact cleaner on terminals and socket connections, then wipe dry. Check for loose, frayed, or damaged wires and repair as necessary before proceeding.
7. 7

   Install new relay
   Position the new relay in the mounting bracket or socket, ensuring correct orientation. Match the terminal configuration to your documented wire positions. If using a mounting bracket, secure the relay with the retaining clip or screw. Ensure the relay is firmly seated and cannot vibrate loose.
8. 8

   Reconnect electrical connections
   Reconnect each wire to its correct terminal on the new relay, following your documentation from step 2. Ensure each spade connector is pushed fully onto the terminal and seats firmly with an audible click. Apply a small amount of dielectric grease to each connection to prevent corrosion.
9. 9

   Reconnect battery and test operation
   Reconnect the negative battery terminal and tighten securely. Turn the ignition to the ON position. Start the engine and allow it to warm up to operating temperature while monitoring coolant temperature gauge. The cooling fan should activate when the engine reaches the temperature switch setpoint of the installed aftermarket fan controller (commonly somewhere in the 180-205°F range, depending on the specific switch used). Listen for relay clicking when fan engages and disengages.

Reassembly

1. Ensure all electrical connections are tight and properly routed away from hot engine components and moving parts
2. Verify relay is securely mounted and cannot vibrate loose during vehicle operation
3. Double-check that no tools or parts were left in the engine compartment

Verification

• With engine at operating temperature, verify cooling fan cycles on and off based on coolant temperature
• Listen for relay click when fan activates - this confirms relay is switching properly
• Check that fan motor runs smoothly without unusual noise or vibration
• Verify no electrical burning smell or excessive heat from relay during operation
• Confirm cooling system maintains proper operating temperature during idle

More procedures for this vehicle