How To Wire An Electric Fan Relay

How to Wire an Electric Fan Relay: A Comprehensive Guide

Wiring an electric fan relay might seem daunting, but with a clear understanding of the process, it's a manageable DIY project that can significantly improve your vehicle's cooling system. This guide will walk you through the steps, explaining the purpose of each wire and offering troubleshooting tips.

Understanding the Purpose of a Relay

Before diving into the wiring, let's understand why you'd use a relay. A relay acts as a switch, allowing a low-current circuit (your car's electrical system) to control a high-current circuit (your electric fan). This protects your car's wiring from the heavy current draw of the fan motor, preventing potential damage and overheating.

Components You'll Need

Before you begin, gather the necessary components:

• Electric Fan Relay: Choose a relay with the appropriate amperage rating for your fan motor. Check your fan motor's specifications for this crucial information. Getting the wrong amperage can be disastrous.
• Wiring Harness: You'll need wires to connect the relay to the battery, fan, and control circuit. Use appropriately sized wires to handle the current. Thicker wires are needed for higher currents.
• Wire Connectors/Crimps: Secure connections are vital. Use appropriate connectors to prevent loose wires that could short-circuit or cause problems.
• Fuse: Protect your circuit by using an inline fuse with a rating appropriate for the fan's amperage. This is a critical safety precaution.
• Electrical Tape: Securely tape all connections to prevent shorts.
• Basic Tools: Screwdriver, wire strippers, crimpers.

Step-by-Step Wiring Instructions

This guide provides a general framework. Always consult your specific relay and fan's instructions for precise wiring details.

1. Identifying the Relay Terminals:

Most relays have five terminals:

• Terminal 85: Ground
• Terminal 86: Power (usually from the ignition switch)
• Terminal 30: Constant 12V power (directly from the battery)
• Terminal 87: Power to the fan
• Terminal 87a: Normally open contact (optional, often unused in fan applications)

2. Connecting the Wires:

• Terminal 30 (Constant 12V): Connect a fused wire directly to the positive (+) terminal of your battery. This provides constant power to the relay.
• Terminal 85 (Ground): Connect a wire to a solid ground point on your vehicle's chassis. Ensure a good, clean connection.
• Terminal 86 (Ignition Switch): Connect a wire to a switched power source (typically from your ignition switch). This allows you to control the fan's operation via the ignition.
• Terminal 87 (Fan): Connect a wire to the positive (+) terminal of your electric fan motor.
• Terminal 87a (Normally Open): This terminal is often left unconnected in a simple fan application.

3. Securing Connections:

Use wire connectors/crimps to make secure, soldered connections where possible. Ensure that all connections are firmly seated and insulated with electrical tape.

4. Testing the Installation:

Turn on your ignition. Your electric fan should now operate when your ignition is switched on. If it doesn't, double-check your connections.

Troubleshooting Tips

• Fan Doesn't Work: Check all your connections and ensure there are no shorts or breaks in the wiring.
• Fan Runs Continuously: The likely cause is a short circuit or a faulty switch in the ignition circuit connected to terminal 86.
• Fuse Blows: This indicates an issue with either the fan motor (possibly a short), or improper wiring.

Conclusion

Wiring an electric fan relay is a worthwhile upgrade for many vehicles. By following this guide carefully and prioritizing safety, you can improve your vehicle's cooling performance and enhance its reliability. Remember to always double-check your connections and use the appropriate amperage ratings for your components. If you're uncomfortable working with electricity, consult a qualified mechanic.