How To Power 120mm Fan With And Without PSU

How to power 120mm fan? You can power it by directly connecting to the power supply or to the adapter if it’s the RGB one. However, both of the methods are pretty easy if you know the steps.

So, in this guide, we will walk you through all the possible methods to power the 120mm fan for your system.

How To Power 120mm Fan: 3 Ways Explained

We will show you here 3 different ways to power a 120mm fan. You can power a fan directly from a computer power supply unit (PSU), the mains, and from a DC battery.

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Method- 1. Power Fan With PSU

There are two common ways to connect fans directly to the computer’s power supply- computer PSU and the manufacturers using a 4pin or 3pin header connector to connect the fan.

1: Connecting Fan With The Plug Matching The Header Connector

If the 120mm fan has a 3pin or 4pin power supply connector, you have to make sure that the plug matches the header connector of the PSU. Here you are going to need-

  • 120mm fan
  • 3 or 4 pin connector

The process is described below-

  • Choose a 120mm fan with a standard 3 or 4 pin that matches the socket end of your PSU.
  • Switch off the power supply of your computer and disconnect all the connection from the CPU
  • Open your CPU with a screwdriver and search for the header connector.
  • Ensure that the plug and socket are orientated correctly before plugging them with each other.
  • Connect 3 or 4 pin connectors to your motherboard header.
  • Check the connection by plugging the CPU into the power supply.
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2: Connecting 3pin Connector To The 4pin Header

If you have a standard 4pin header in your PSU, but your fan has a 3pin connector, it is also possible to connect the fan.

  • Take a 120mm can with a 3pin connector.
  • Switch off the power supply.
  • Disconnect all the connection from the CPU.
  • Open your CPU with a screwdriver and search for the header connector.
  • Ensure that the plug and socket of the connector are orientated correctly before plug them into each other.
  • Plug the 3pin connector into the 4pin Header.

if you need can check how to connect case fans to PSU with step by step guide.

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Method- 2. Power 120mm Fan From Main

A 120mm fan can be powered from the main line also. To connect the fan, you are going to need an adapter or a LED driver. Here we are describing both.

1: Connect With An Adaptor

To power a 120mm fan from mains using an adaptor, you are going to need-

  • 120mm fan
  • 12v AC to DC power adapter
  • Wirecutter

The process is as follows-

  • Take a 12v AC to DC power adapter.
  • Cut one end of the adaptor and the fan with a wire cutter.
  • Connect the red wire with the red wire and the black one to the black.
  • Secure the connection with electric tape.
  • Check all the connections before plugging into the main.
  • Plug the adaptor to the main.
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2: Connect With A LED Driver

In this method, you need-

  • 120mm DC fan
  • an LED driver
  • power cord

The connection process is as follows-

  • Get your 120mm 12v DC fan.
  • Cut the connector end with a wire cutter.
  • Take a LED drivers that voltage should be 12v or less.
  • Connect the fan to the output marked on the driver. The red wire of the fan with the red wire of the driver and the Black wire to black.
  • Connect a power cord to the marked input side of the driver to plug your fan into house outlets.
  • Recheck the connection.
  • Now, plug into the fans to the mainline.
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Method- 3. Power 120mm Fan From A Battery

To power a 120mm fan with a battery, you need-

  • 120mm DC fan
  • A 9v battery

The steps for this process are-

  • Take a 120mm fan.
  • Cut the connector of the fan from the edge of the wire.
  • Strip ½ inch of the wires.
  • Add red wire clip to the red wire and black wire clip to the black wire.
  • Hook up the negative clip to the black clip to the battery and the positive or red clip to the positive clop of the battery.

Must Double-Check All Connections Before Powering Up

Always recheck all the plugs and connections whether they are assembled correctly or connected to the correct pins. Try to proceed slowly and carefully while working on the connection of a computer.

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How do I connect my 120mm fan to my PSU?

Just ensure the 3 or 4 pin connector of the PSU that matches the 120mm fan plug, connect it. Or, you can also ensure connecting to the exact header pin connector.

Can I plug a 3 pin fan into a 4 pin?

Yes, you can connect the 3 pin fan into a 4 pin header. The only thing here lacks is the PWM mode of the fan speed.


To cool down a computer CPU while you are working is very important. Excess heat can cause damage to your CPU. For this, you may need to use a fan.

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A 120mm fan works well for this purpose. It is possible to power a 120mm fan from PSU by connecting to a motherboard or directly from the mains or from a battery.

In this article, we have described different processes of how to power 120mm fan. This will help you to power with a PSU or without a PSU.

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Michael Oliver

The blending of his writing savvy with long-term technological practices with IOS and MAC programs always tickle him find out a quick fix to the problems. So, he wishes to share his fixes and discovers with all through these fixing guides. Also! He has won the market with his entrepreneurial spices backed by spurring paces to meet new challenges.

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