How to Replace Fan Relay in 2005 Subaru Legacy: Full Guide

Replacing the fan relay in a 2005 Subaru Legacy is crucial for maintaining optimal engine temperature and ensuring that the cooling system functions correctly. A failing relay can cause the cooling fan to run intermittently or not at all, risking overheating. This guide offers a comprehensive, step-by-step breakdown for DIY fan relay replacement to get your Legacy running smoothly again.

Tools and Preparations for Replacing the Fan Relay

Tools Needed

• Screwdrivers and pliers: Basic tools for accessing and removing the relay from the fuse box.
• Electrical multimeter: To test the old relay for continuity and determine if it is indeed faulty.
• Replacement relay: Ensure the replacement relay is compatible with the 2005 Subaru Legacy.

Precautions

• Safety first: Before working on any electrical component, disconnect the battery. This prevents accidental short-circuits and minimizes the risk of electric shock.
• Handling relays with care: Relays are sensitive components. Be gentle during removal and installation to avoid damaging either the relay or the socket.

Locating the Fan Relay and Fuse Box in Your Vehicle

The fan relay in a 2005 Subaru Legacy is typically found in the engine compartment fuse box. Accessing the fuse box involves:

• Opening the hood and locating the fuse box on the left side of the engine bay.
• Removing the cover to reveal the relays and fuses. The fan relay should be marked on the cover diagram for easy identification.

Symptoms of a Failing Fan Relay in the 2005 Subaru Legacy

Signs of Relay Failure

Identifying a failing fan relay can save time and prevent more costly repairs. Common signs include:

• Engine overheating: If the cooling fan isn’t turning on, the engine temperature can rise quickly, especially in warm weather.
• A/C problems: The fan relay helps regulate cooling, which affects A/C performance. Issues here may be linked to a bad relay.
• Unusual fan behavior: The fan may stay on longer than necessary, cycle irregularly, or fail to start altogether.

Diagnosing a Bad Fan Relay

Use an electrical multimeter to check if the fan relay is functioning. This test involves:

• Setting the multimeter to continuity mode and attaching it to the relay’s terminals.
• A lack of continuity indicates the relay is likely faulty and needs replacement.

Step-by-Step Guide to Replacing the Fan Relay

Step 1 – Accessing the Relay Box

1. Open the engine compartment: After ensuring the engine is cool, open the hood and locate the fuse box.
2. Identify the fan relay: Use the diagram on the fuse box cover to locate the fan relay. It should be labeled clearly.

Step 2 – Removing the Old Fan Relay

1. Gently pull out the relay: Using pliers or your hand, carefully pull the relay out of its socket. Avoid excessive force.
2. Inspect for damage: Check for any signs of corrosion or damage on both the relay and the socket. Clean the socket if necessary.

Step 3 – Testing the Old Relay

1. Use a multimeter: Attach the multimeter leads to the relay’s terminals.
2. Check for continuity: If there’s no continuity, the relay is faulty and should be replaced.

Step 4 – Installing the New Fan Relay

1. Align and insert: Position the new relay above the socket and gently press it into place.
2. Ensure a proper fit: Confirm the relay is securely seated with no gaps.

Step 5 – Testing the New Fan Relay

1. Reconnect the battery: Once installed, reconnect the battery.
2. Test the fan: Start the engine and observe the fan behavior. It should cycle on and off as needed.

Common Issues Post-Replacement and How to Resolve Them

Fan Still Not Running or Cycling Incorrectly

If the fan doesn’t operate correctly, the problem may lie in:

• ECU or wiring issues: The ECU may fail to send signals to the relay due to wiring issues or faults within the ECU itself.
• Relay compatibility: Confirm the relay is compatible with the 2005 Subaru Legacy to avoid issues.

Persistent Overheating After Replacement

Other cooling system components could be the cause, including:

• Thermostat: A faulty thermostat can lead to overheating by not opening and closing properly.
• Radiator: Any clogs or leaks in the radiator can reduce cooling efficiency, causing the engine to overheat.

Maintaining Your 2005 Subaru Legacy’s Fan Relay and Cooling System

Routine Checks and Preventive Maintenance

To keep your Legacy’s cooling system running smoothly:

• Inspect regularly: Periodically check the fan relay, fuses, and related components for signs of wear or corrosion.
• Clean contacts: Use a contact cleaner on the relay socket to prevent corrosion.

When to Consider Professional Help

For complex electrical issues, professional diagnostics may be necessary. Seek a reputable Subaru mechanic if:

• Wiring issues persist: Experienced technicians have the tools to diagnose wiring or ECU issues.
• Relay replacements are frequent: Recurrent issues may signal an underlying problem that requires advanced testing.

Frequently Asked Questions (FAQs)

How often should I replace the fan relay?

Relays generally don’t require regular replacement unless they show signs of wear or fail. However, older vehicles may need more frequent checks.

Can a faulty fan relay affect other systems?

Yes, the fan relay impacts the cooling system, which in turn affects engine performance and the A/C system.

Is there a recall for the 2005 Subaru Legacy’s fan relay?

Some Subaru Legacy models had recalls related to the ECU and fan relay. Check with a Subaru dealer to see if your model is affected.

Conclusion

Replacing the fan relay in your 2005 Subaru Legacy is a straightforward task that can significantly improve engine cooling efficiency and performance. With the right tools, a bit of preparation, and careful steps, you can complete the process at home, saving time and money while maintaining your vehicle’s cooling system health. Regular maintenance checks will help prolong the lifespan of your Legacy’s fan relay and prevent overheating issues.