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PC Fan Speed Control Guide

PC Fan Speed Control Guide

Here is a guide to installing a PC fan speed controller, and the various options you have in software and hardware. On this page:

1. About fan speed control issues
2. Speedfan fan control software setup guide
3. Comparison with i8KfanGUI fan control software for Dell computers

1. Why you might need fan speed control

There is one major and one minor reason:
  • Fans normally run at 100% speed, which is noisy and unnecessary. In any case the fan speed should be varied according to temperature.
  • Fans running at 100% will draw unnecessary power
The CPU cooler fan is often too noisy. If your PC is noisy then the chances are that it's the CPU fan - you may even have a 'screamer', and then the choice is to replace it, or cut the speed, as it just isn't necessary to run at full speed all the time - if ever. Normally the CPU cooling fan only needs to run at about 75 or 80% just when the PC is under heavy load, since fans are over-specified.

Case fans can often run even slower, at about 50 or 60% speed, as they work fine like this. They are usually much quieter than the CPU fan anyway, but cutting the unnecessary speed has the benefits of less total noise, and lower power consumption.

Best fan speed control option

The #1 choice has to be a fan speed controller program such as Speedfan or i8kFanGUI, which are both freeware. There is an install and configuration guide for Speedfan lower down.
If the fans have to be wired direct from the PSU instead of via the mainboard and its fan control abilities - as some do, as there are occasionally more fans in the case than there are slots on the mainboard - then hardware options such as a fan speed control panel can be used.

Laptop fan speed control

This guide is for PCs, not laptops. Laptops are built differently: a laptop is not a PC in a small case. The biggest difference is in the mainboard - there are no facilities for plugging in fans, reading temperatures, and controlling fans. Because of this there is only one way to control laptop fan speeds: to utilise the two existing fans (CPU and case), and change their speeds by adjusting BIOS operation. This is not an easy operation and the only make of laptops this aftermarket solution is available for is Dell. The only other laptops that have fully-variable user control of temperature and fan speed are expensive models such as some Alienware examples.

For this reason a Dell laptop does have some advantages for those who have found that they prefer total control of temperatures / fan speeds / noise, as the Dell laptop fan speed app i8kFanGUI can be used. We use Dell laptops although we would not buy a Dell PC, since they are not PCs in the strict sense of the word (they use proprietary components - you cannot upgrade either the PSU or the mainboard by purchasing a better 3rd party item, for example, because the power connections are non-standard). For upgrade or repair you must go to Dell or know exactly what you are doing.

Laptops are also different in that most people would not want to get involved with upgrades or repairs, in complete contrast to a PC, where anyone who has a wristband anti-static earth strap can open it up and change components. 

What fans does a PC have ?

There are usually 3 or 4 fans:
  • The CPU cooler fan
  • Case fan #1
  • A case fan #2 if fitted (though it might be paralleled-up with fan #1)
  • The PSU fan
The CPU processor cooler fan is usually the noisiest, as the case fans and especially the PSU fan are normally fairly quiet.

Hard disk cooling fan

Note that hard disks also need a fan for cooling, however this is never built-in, it is always external. There is always some arrangement to provide airflow over a disk because otherwise it would overheat.

Therefore the disks are usually placed behind the air vent, or behind a case fan, so that the airflow cools them. Even just the PSU fan pulling air through will cool the disk/s sufficiently.

A hard disk in a PC case normally runs at 35 degrees C or less, due to the through-case airflow (32 C is common). With poor airflow it will go up to 45 or 50C, which is about the hottest you should allow otherwise reliability is affected. In a non-cooled environment such as an external USB hard drive enclosure with no fan, the disk can go over 70C, and obviously this has to mean that it is disposable and the data on it is also disposable.

Negative case pressure

Originally, PCs were cooled with a positive pressure system: the main fan was at the front, and blew into the case, with a vent at the back, resulting in positive pressure. Now, this has given way to a negative pressure system, with the fans at the back - the PSU and the case fan - acting as extractors and sucking the air out, which is slightly more efficient. There may be another fan at the front, assisting.

The airflow from the front vent passes through a filter and over the hard disk (or disks), cooling it. Make sure to keep the front air filter clean as it gets clogged by dust fairly quickly.

The airflow then passes the CPU and helps to take away the hot air from the processor cooling systems, usually a fan on a copper mount, before exiting through the rear case fan, or through the PSU and fan.

What speeds do fans run at ?

The most common speed is 5,000 rpm, and they are set to run at 100% by default. Just 50 or 60% of full speed is often sufficient, and as the real noise range is above 80%, this is of great benefit.

How to fix fan noise ?

If you have a noisy fan or fans, there are 4 options here that can be tried in turn:
  • Free software - a fan speed control program
  • Hardware - a fan speed controller panel
  • A resistor in the fan/s power line
  • Buy a quiet fan (or several quiet fans) and install them

What is a fan speed control program ?

Most fans can be controlled by a software speed control application. This is usually the best solution as it's a free program, and therefore it can be tried for free. It works on most Windows versions, on most mainboards. The mainboard (aka motherboard) is the critical part as this has the temperature sensors, the fan control hardware, and the fan power plugs. The fan controller program works with most mainboards. It's a small free app of less than 2MB.

It will normally quieten down the biggest noise source, which is the CPU fan. It may not be able to take care of case fans, as they are sometimes wired direct to the PSU (power supply) - but this isn't a problem as they are usually much quieter than the CPU fan anyway.

Hardware options for fan speed control

1. Fan controller panel
If there is a fan that can't be controlled by software, then you can get a physical, hardware controller panel that slots into one of your 5.25" optical drive bays. In other words it fits in next to your CD / DVD drives, if you have a spare slot. If not, you can get a 3.5" one that fits in a spare Floppy Disk slot.

The controller has a panel with temperature readouts and fan speed dials -or just the dials for cheaper versions and the small 3.5" version.

2. Fan power line resistor
An even cheaper option is to simply put a resistor (or a variable resistor) in the positive* power line to each fan - this costs pennies and works as well, though you need the parts and tools.

Unless you use a variable resistor then you might find you need to swap out the resistor for another, if you need the basic fan speed higher or lower. And of course you can't vary the speed according to temperature with this method, unless you fit variable resistors and drill holes in the case for the knobs.

* It is best practice to put switches or components in the positive line (marked + or red) to equipment. In fact it will work as well in the negative line, but it is poor workmanship to switch or control the negative lines (marked - or black).

4. Quiet fans
OK, an obvious way to fix a noisy fan is to replace it with a quiet fan. But it isn't that simple. Firstly, of the 3 main fans, only the CPU fan is normally a noisy one. It is by far the most expensive to replace - if you can find a replacement. You'll probably need an entirely new CPU cooler. It's simpler to slow it down.

The PSU fan is usually quiet - but replacing it if it's noisy is a job for a tech, not DIY. Also, check first that it doesn't actually have a fan speed control knob on the case, many better PSUs do (at the back of the PC case, check for a very small serrated knob by the main power plug).

The case fan is normally quiet as well - especially if you slow it down, as it hardly ever needs to run hard. If there are two, then disconnect one, it's not needed unless you are running a 3GHz CPU on video editing fulltime. Make sure to monitor the mainboard temperature before and after you do this, just to make sure it's OK.
Ideally you will have some sort of warning in place so that high temperatures are seen. Mainboard monitor apps often come with the board and should be installed. Alternatively, the fan speed controller software has a similar arrangement.

Best fan speed controller

Because of all these factors, the speed control program is the best option. If it doesn't work for some reason, then go to Plan B. I have tried the software on old mainboards and it works just fine. For brand new ones out this week it should work just as well, since the temperature sensors are standard kit. If you need help with the latest Windows7 - whizzo mainboard - eSATA RAID disk combinations etc, then just use the integral Report form within the app, the developer wants info on new kit and will help you get your new system to work.

The fan speed control program recommended here is well-engineered and should work with 95% of fans on 95% of systems, if not better. The great benefit is that fan speeds are automatically varied according to temperature. Here are the download details:

Program: Speedfan 4.39, from almico.com
Download page: PC fan speed controller

The download link on the page is a tiny text link that is easy to overlook, see this image if you can't find it.

Speedfan download  Speedfan download - link location

Dell fan speed controller

An alternative for Dell PCs or laptops is the excellent i8kfangui from diefer.de. It has about the worst name for an app ever seen as it's hard to remember or even decipher, but does the job well. You can download it here:

Dell fan control program

The main difference to Speedfan is that i8kFanGUI for Dell doesn't vary the fan speeds vs temperature, you set several fan 'profiles' and then choose one to run with. These simply set a temperature that a given fan comes on at, when it will run slow or fast. It cuts off when the temp drops. It does have a better system tray temperature readout display than Speedfan though.

If the PC or laptop (and especially for laptops) is working hard, you can change to a fan speed profile with a lower cut-in and a longer fan run. Speedfan is better, however, as the temperature control is automatic, varying the fan speed according to the temperature. The fan is always on at a low speed. In addition you can fully configure fans, speeds, and temperatures.

For this reason you should install Speedfan first, then try i8kFanGUI if for some reason you don't like Speedfan. One reason might be that Speedfan is not easy or straightforward to set up for non-techies, and if you have a Dell laptop and are a non-techie then i8kFanGUI is a bit more of a plug-n-play solution.

Speedfan vs i8kFanGUI

If you have a Dell then you can use either. Here are the pros and cons.

- Full auto temperature control - fan speed is varied according to temperature
- Fan speeds can be tested fully, and the lowest possible speed chosen
- Should work with all hardware

- Hard to set up on a Monday morning

- Easy to set up - just use the defaults and run it (more or less)
- Very good for Dell laptops
- Also acts as a resource meter: CPU load and CPU speed can be displayed

- Only works on Dell hardware
- Fixed fan speeds
- 'Temperature control' means slow or fast fan speed
- Best for laptops, not so good for PCs

2. Speedfan set-up guide

The current version at time of writing is Speedfan 4.39. You can fully control all aspects of fans, speeds and temperatures. The fans automatically and independently vary speed in order to cool their associated equipment.

For example you can allocate Fan 1 to CPU cooling, rename it to CPU Fan, set the fan speed to 60% as the default run speed, set 80% as the full speed, set the desired CPU running temperature, and finally set an 'emergency' temp that if the CPU reaches it, the fan will go to full speed (100%). And as soon as CPU temperature falls, the fan speed gradually drops, after a small time lag.

You would think that mainboard manufacturers would provide these controls since their boards contain all the hardware that is used - the temperature sensors, the fan voltage controllers, and the fan power sockets. They often do of course, but their versions either don't work or are poorly implemented.

For example on one of my PCs with an expensive MSI mainboard, there is what looks like a very comprehensive voltage and fan status and control app. Unfortunately the fan controller (of which there is only one anyway) doesn't work. The readouts are pretty but you can't do anything with them. So as per usual you need 3rd-party specialists to do the job properly, and when you look at the level of sophistication of Speedfan, it's clear that mainboard software staff are unlikely to be able to produce anything at that level. It's very smooth in all respects, very comprehensive, and works with any hardware. It has all sorts of options for voltage status and even clock operations, if you want to go that far.

Install Speedfan

Just download from the link above, and install as per normal. On startup Speedfan is running on default configs, and this means:
  • No fan speeds are controlled
  • No hardware control or alterations are operative yet
  • There is a single temperature readout in the System Tray, which will usually be the case temperature (ambient temperature), the overall internal temp as measured on the mainboard.
We will probably want to change these default configs, as follows:
  • Prioritise for the CPU temperature as that is normally the 'screamer' fan
  • Change the systray temp display to the CPU readout
  • Change the display colour
  • Set up the fans / speeds / temperatures required

System tray temperature display

First we'll fix the systray readout. Job 1 is to make it easier to see, so we'll have blue text on a yellow background.
  1. Right-click the systray temp display
  2. Select Restore, this opens the main config window
  3. Hit the Configure button near top right
  4. On the Configure window that opens, select the Options tab
  5. Hit the spinbox control at the right, on the jump menu for Icon background
  6. Select the yellow bg as this gives best visibility
  7. Blue text is already selected by default
  8. Leave all other options as-is
  9. Hit OK to save and exit
Now you will have a blue text on yellow bg display in the systray, probably with a temp of around 35C for a PC or 45C for a laptop, if your system is running as normal. This is the mainboard average temp or case internal temp if you like.

You might prefer to have the CPU temperature as the primary display, though, as that is the fastest to change under load and also involves the loudest fan. To do this:
  1. Right-click the systray temp display
  2. Select Restore, this opens the main config window
  3. Hit the Configure button near top right
  4. On the Configure window that opens, select the Temperatures tab (which is the first page)
  5. In the main pane you will see a list of temperature lines
  6. Under the heading Sample you will see the actual system temperatures
  7. Pick the highest temperature there - that will be the CPU
  8. If there are two about the same, then look at the second column, Chip
  9. Under Chip, see which of those two temps has 'Winbond' there
  10. Select that temperature / hardware line, by clicking on the name, eg Temp 1
  11. Drag that whole line up to the top of the page, if it isn't there at present
  12. Double-click the name Temp 1 to select the name text (it blues out), then change it to CPU
  13. Down on the window's status bar, at lower right, select 'Show in tray'
  14. Click OK to save and exit
Now you have the CPU temp showing in the systray, and with it at the top of the page in the fan temperature configs.

If there are two lines with the same temperatures, then use the line with the Winbond chip - the other one may be an LM75 which is just a clone, the main one is the Winbond temperature.

If you have 2 CPUs then the process is doubled.

Configurations for Speedfan are fairly complex. We might insert a section on the procedure here, later.

Speedfan tips

  • To work on a fan and its configs, turn all the other fans off, then wind down the fan speed of the one in question until it's hardly audible. Then, when you change a setting that affects it, you can hear the difference as it speeds up.
  • The important sensor for each temperature is the Winbond chip, the LM75 is just a mirror of that.
  • Set the CPU fan speed to 60% at first, this should be about right.
  • See what temperature the CPU stabilises at with a 60% fan speed, then set the "Desired" temperature to 2 degrees above that.
  • Adjust those two settings to keep the CPU temp under 60 degrees and preferably as near to 55C as possible (or lower if that can be done at an acceptable minimum fan speed and/or fan loudness).
  • Lower temperatures, wherever measured, mean a higher basic fan speed therefore more noise.
  • 60% is a good basic fan speed to trial first.
  • 80% is a good max fan speed, if this doesn't quickly pull temperatures down it is unusual.
  • The 'Warning' temp is when the fan will go to 100% speed.
  • For a CPU you could try Desired Temp as 56C and Warning Temp as 63C.
  • The Desired Temp should be 2 degrees above a temperature achieved easily, ie with a fan speed of 60 or 65%.
These tips apply to setting up Speedfan on a normal work PC. If you are using the computer for video editing or gaming, and/or run it overclocked, then you will have to accept higher fan speeds and longer fan runs.

Some of the topics here are best fan speed controller, speedfan guide, control fan speed, control CPU fan, quiet fan, noisy fan.

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