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HomeTips & GuidesElectric Fan Relay Wiring – With Detailed Step and Troubleshooting Tips

Electric Fan Relay Wiring – With Detailed Step and Troubleshooting Tips

About Electric Fan Relay Wiring: Electric fans remove warm air from your car by improving circulation, ensuring comfortable working temperatures. 

While fans are strong and durable, sometimes their motor does not get enough power to work properly. 

For this reason, you need a relay to ensure enough power and control to your fan, improving its efficiency. 

In this article, I will show you detailed electric fan relay wiring steps and some vital troubleshooting tips.

What Is an Electric Fan and Relay

An electric fan features a motor that spins some fan blades, which can provide cooling. Technically, the motor in the fan requires enormous power to function properly. 

On the other hand, a relay refers to a device that amplifies and controls electric current. 

The relay is a bridge that gets power from the source ( car battery) and redistributes it to the fan motor. 

This functionality ensures an efficient power distribution to the motor while helping control the fan effectively.

An example of a separate relay

An example of a separate relay

How Does a Relay Work In a Fan?

The relay has components like a coil, a switch, and contacts. Now, the magnetism of the coil creates a magnetic field, which in turn attracts the contact to complete the circuit. 

The current flows from the source to the fan motor, and the fan works. When the switch is off, coil demagnetization occurs, breaking the circuit, and the motor stops. 

A relay improves efficiency, ensures no heat build, and reduces switch load. All these benefits allow fan longevity, enhanced control, and optimal fan speed, depending on temperature.

How to Wire Electric Fan with Relay

Now that you know what fan and relay are and how they function together, let’s now discuss the wiring process:

Required materials

  • Electric fan which is compatible with your systems and suits your cooling requirements.
  • Relay with the correct amperage rating (same or more power) to handle your fan motor needs. 
  • A reliable power source such as a car battery based on your system.
  • Quality wire connectors such as ring terminals and spade connectors are used to ensure reliability and safety.
  • Electrical tape for protecting and insulating naked wire connection thus preventing electrocution or short-circuiting.
  • Install a fuse holder with the correct amperage fuse rating (depending on your motor) on the power source to prevent overloading.
  • Wires with the correct gauge depending on the motor amperage.
  • Handtools such as a crimping tool, wire cutter, pliers, and screwdriver to facilitate the wiring process.

 An isolated fuse holder photo

 An isolated fuse holder photo

Specific Steps

After you have gathered all the tools and the material you require, let’s now dig deep into the steps:

Install the Electric Fan

  • The first step in this process is to install the electric fan in the place of your choice. Choose an ideal location considering accessibility, airflow, and enough space for blades to rotate without obstructions.
  • Now place your fan in your ideal location, trace its installation holes, and mark them with a pencil.
  • Use an appropriately sized drill bit and make pilot holes on the marks you drew earlier.
  • Once completed, align the mounting bracket with the pilot holes and secure it with the appropriate screws to ensure stability.

Prepare the Wiring

If you have installed the fan successfully, it’s time for wiring preparation. 

In this process, identify the most suitable wiring route from the source to the fan, considering safety, accessibility, and proximity.

 Now measure your required wire length, adding a few inches for flexibility. 

From there, use the wire stripper to remove enough insulation at the wire end to facilitate connection. 

Then, attach your chosen wire connectors and crimp based on the manufacturer’s guidelines. 

In the next optional process, use the labeling tape to mark the wires, especially if you use many. 

Doing so helps in identifying them later in the process.

 Finally, organize your wires using a wire loom or cable ties to avoid tangles and ensure neatness.

Cables in a wire loom

Cables in a wire loom

Connect the Relay to Power

First, choose an appropriate and secure installation location based on where the fan is. 

Then, mount the relay using bolts or a strong adhesive to ensure it’s secure and tight. 

Now inspect the relay terminal and choose terminals 30, 85, 86, and 87. 

Use the appropriate wire connectors and hook one power wire to terminal 30 on the relay.

 Once done, ground the device by connecting its terminal 85 to a suitable grounding such as car the chassis. 

Lastly, connect the other wire of the power supply to terminal 86 on the relay, and it’s now powered.

Connecting the Fan to the Relay

You will start by identifying motor power wires. These wires have color codes: black/red for power and blue/green for grounding. 

Connect the electric motor power wire to this 87 terminal on the relay and ensure the connection is secure. 

From there, connect the ground wire to an appropriate grounding as you did for the relay. 

Once done, inspect the connection for loose connections and exposed wires and secure them properly.

Wiring Process Finalization

The final step ensures the completion of the remaining connections and proper inspection to ensure functionality. 

Here, start with installing the fuse holder between the relay and the power source. Then, put your wires in a wire loom for proper organization and avoid cost tangling. 

While here, utilized the insulating tape to seal any naked connections to protect them. Once everything is in place, power your fan to test the connection.

 Lastly, secure the wires properly and close any covers you removed during the wiring process.

Troubleshooting Common Issues

Although connecting the fan with a relay seems easy, sometimes you may run into fan problems. When that happens, I recommend using the following solution:

  • Ensure enough power from the source and that no fuse is broken.
  • Inspect the wiring you made to ensure no loose connections, disconnections, or damaged wires.
  • Examine the relay to ensure it makes clicking sounds when the fan is on. If not so, it might be faulty and need replacing or repair.
  • You may also disconnect the motor and test it individually to ensure it is spinning. 
  • Your fuse may also blow regularly, which you can solve by ensuring it’s of proper rating. Check no exposed wires that may cause short circuits and that the relay does not malfunction to draw excess current.
  • Another problem is vibrations and noise in the fan, which you can solve by cleaning the blades for obstructions. You may also ensure secure mounting or replacing the motor if the issue persists.

Troubleshooting a connection

Troubleshooting a connection


Now, you may rest because you have connected your fan with the relay successfully using the steps above. 

While this can enhance fan functionality, efficiency, and control, when improperly done, it can destroy the fan or relay.

Hi I am Christa, sales manager of Cloom.

I have extensive expertise and experience in wiring harnesses and I believe I can help you.

And we have a very professional technical team who can clearly understand the customer’s needs and give professional suggestions and solutions after receiving the drawings.

If you also have wiring harness needs, please send me the drawing so that we can give you our quote and start our business.

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