The OEM part number for a 1987 C4 Corvette cooling fan relay is 14089157

Chevrolet used part number 14089157 as the original equipment manufacturer (OEM) relay for the cooling fan circuit on 1987 Corvette C4 models. This is a four-terminal relay that controls power to the electric cooling fan based on engine temperature signals from the coolant temperature sensor. If you are replacing a failed relay, this number will match your original part exactly.

The relay sits in the engine bay fuse and relay block, typically mounted on the driver's side inner fender or near the battery. When the engine coolant reaches a set temperature (usually around 195°F), the temperature sensor triggers the relay to close, sending power to the cooling fan motor. A failed relay will prevent the fan from running, causing the engine to overheat even when the car is idling or in traffic.

Key Takeaways

  • The original 1987 C4 Corvette cooling fan relay part number is 14089157, a four-terminal relay mounted in the engine bay fuse block.
  • The relay activates when coolant temperature reaches approximately 195°F and sends power to the electric cooling fan motor.
  • A failed relay will prevent the fan from running, leading to engine overheating at idle or in slow traffic.
  • Aftermarket relays with the same terminal configuration and amperage rating can substitute for the OEM part at lower cost.
  • Testing the relay with a multimeter or swapping it with a known good unit can confirm whether the relay or another component is causing fan failure.

Where the relay is located and how to access it

The cooling fan relay on a 1987 C4 is housed in the main fuse and relay block on the driver's side of the engine compartment, typically mounted to the inner fender wall near the battery or on the firewall itself. The exact location varies slightly depending on whether your car has the base L98 engine or the optional L98 Tuned Port Injection setup, but the relay block itself is always in the same general area. You will need to remove the plastic cover from the fuse block to access the relays inside.

To locate the correct relay within the block, consult the diagram printed on the underside of the fuse block cover or in your owner's manual. The cooling fan relay is usually labeled clearly. Once you identify it, pull the relay straight out of its socket. The relay is a small rectangular component with four metal terminals on the bottom. Replacement takes less than five minutes and requires no special tools beyond a flashlight to see inside the fuse block.

Aftermarket and cross-reference options

If you cannot find the original 14089157 relay, several aftermarket suppliers stock equivalent relays under different part numbers. Bosch, Standard Motor Products, and Wells all manufacture relays that fit the same socket and perform the same function. The key is matching the terminal configuration (four terminals) and the amperage rating (typically 30 amps for the C4 cooling fan circuit). Most auto parts stores can cross-reference 14089157 to their own inventory within seconds.

Aftermarket relays are usually 40 to 60 percent cheaper than OEM Chevrolet parts and carry the same warranty. The main trade-off is longevity—OEM relays often last longer in high-heat engine bay environments, but a quality aftermarket relay should give you several years of reliable service. Always verify the amperage and terminal count before purchasing, as installing the wrong relay can damage the fan motor or wiring harness.

How to test whether the relay is actually the problem

Before replacing the relay, confirm it is the cause of your cooling fan failure. The simplest method is the swap test: locate another relay in the fuse block with the same four-terminal configuration (such as the fuel pump relay), remove it, and install it in the cooling fan relay socket. Start the engine and let it warm up. If the cooling fan now runs when the engine reaches operating temperature, the original relay is faulty and needs replacement.

If you have a multimeter, you can test the relay without swapping. Set the meter to resistance (ohms) mode and touch the probes to the two coil terminals (usually the outer two terminals). You should read between 60 and 100 ohms. If the reading is infinite or zero, the coil is open or shorted and the relay has failed. You can also listen for a click when the engine warms up—a working relay will audibly click as it closes, while a failed relay will remain silent.

Common reasons a 1987 C4 cooling fan relay fails

The most common cause of relay failure in a 1987 C4 is heat exposure. The engine bay of a Corvette runs hot, and the relay block sits in direct line with engine heat. Over 35+ years, the internal contacts corrode and the coil insulation breaks down, causing the relay to stick open or fail to energize. Moisture and road salt can also corrode the terminals, preventing good electrical contact even if the relay itself is functional.

A second cause is a shorted or stuck cooling fan motor. If the fan motor draws too much current, it can overheat the relay contacts and cause them to weld together or burn open. If you replace the relay and it fails again within a few weeks, have the cooling fan motor tested before installing another relay. A failing motor will destroy a new relay just as quickly as it destroyed the old one.

Wiring and electrical circuit overview

The 1987 C4 cooling fan circuit is straightforward: the coolant temperature sensor (mounted on the engine block) sends a signal to the relay coil when coolant temperature rises. The relay coil energizes, closing the switch contacts and completing the circuit from the battery to the cooling fan motor. The fan runs until the coolant cools below the setpoint, at which time the sensor signal drops, the relay de-energizes, and the fan stops.

A fuse (usually 30 amps) protects the circuit between the battery and the relay. If the fuse is blown, the relay will not receive power and the fan will not run, even if the relay itself is good. Always check the fuse first before assuming the relay is bad. The fuse location is marked in the fuse block diagram. If the fuse blows repeatedly after replacement, a short in the wiring or a failed fan motor is drawing excessive current and must be repaired before installing a new relay.

Frequently Asked Questions

Can I drive my 1987 C4 if the cooling fan relay is bad?

Not safely for long distances. Without a working cooling fan, your engine will overheat during idle or slow traffic, even if the radiator and coolant level are fine. You may be able to drive at highway speeds where airflow through the radiator is sufficient, but stop-and-go driving or sitting in traffic will cause overheating within 10 to 15 minutes. Replace the relay before the engine reaches critical temperature and causes internal damage.

Is the 1987 C4 cooling fan relay the same as other Corvette years?

No. Relay part numbers changed between model years and engine options. A relay from a 1988 or 1989 C4 may not fit the 1987 socket, and relays from earlier C3 Corvettes are completely different. Always verify the part number matches your specific year and engine before purchasing. Your local Chevrolet dealer or a parts cross-reference database can confirm compatibility.

What happens if I install a relay with the wrong amperage rating?

An undersized relay (lower amperage) will overheat and fail quickly because it cannot handle the current draw of the cooling fan motor. An oversized relay (higher amperage) will not protect the circuit properly and may allow a short or motor failure to damage the wiring harness before the fuse blows. Always match the amperage rating printed on the relay case to the original specification, typically 30 amps for the C4 cooling fan circuit.

Do I need to reprogram anything after replacing the relay?

No. The relay is a passive electrical component with no computer programming or settings. Remove the old relay, insert the new one, and the circuit will function when ready. The engine computer does not need to be reset or reprogrammed. If the fan does not run after relay replacement, the problem lies elsewhere in the circuit—check the fuse, temperature sensor, and fan motor.