Replacing PSU and case fan

  **nada** 20:08 10 Jul 2003

My PSU and case fan have become annoyingly noisy over time and I've decided to do something about it. I've tried oiling both but that hasn't made much difference.

The problem is that the PSU fan has a non standard two pin connector, but the fan itself is just the same as a normal case fan (it is 80mm x 80mm x 25mm click here - it's the ASB0812HH). So the question is, will a normal case fan with 3 pins (I can only find 3 pin fans on the net) work if I wire it as necessary (what does the third white pin do on fans anyway).

Finally for the case fan, can you recommend a rough air flow that I need. It is cooling both the processor and whole case in my Dell Dimension 8100; by special plastic ducts that surround the processor (I can't find any specifications for this fan in my PC). Would 40CFM be about right, or should I get one of these fans with a temperature sensor? (By the way this fan is a standard 90mm fan with a 3 pin connector)


  Psiman 20:35 10 Jul 2003

Just had a look at my Dell Dim. 8100 (P4 1700)and the air flow is very low, 15 - 20 cfm I would guess. For a Dell P4 machine 40 cfm with dedicated CPU air ducting would be way too high and noisy. If you buy something in the mid-twenties you should be OK. (Monitor your CPU temp though).

If you have a third wire its usually for data aquisition; nice but not needed.

Your case ventillation is not solely carried out by your PSU cooling fan, the case ventillation load is shared with the PSU fans.

Trust this helps.

  Psiman 20:48 10 Jul 2003

For my second to last "PSU" in the above post read "CPU".

BTW for quiet fans similar to those used by Dell click here

  **nada** 21:05 10 Jul 2003

Thanks for the response.

That confirms what case fan I will be getting.

Just to check about the PSU fan; so I buy a 3 pin fan, snip the wires and solder the black and red cables to the plug of my old fan (2 pin no standard plug), by cuting the plug off my old PSU fan - if that makes sense.

  **nada** 21:06 10 Jul 2003

Oh, I forgot to say; what are the two extra pins on a 4 pin fan, and why are they needed/what do they do?

  Ironman556 21:29 10 Jul 2003

I think that you're referring to the type of connector on a fan that would connect to a standard cd rom? If you are I'm pretty sure the third and/or fourth pin is left alone. If you run out of fan connectors, you have an alternate way of powering the fan.

  Psiman 21:32 10 Jul 2003

A 4 pin fan connector is usually equipped with a 'molex' type connector, which is the type of power connector used for a HDD or CD-ROM drive. I use these fans with this sort of connector for case ventilation only. A CPU fan normally has to be powered of the motherboard for various equipment safety and BIOS interlock reasons.

As to cutting an soldering on your plug to your new fan, I shall gratefully decline to comment.

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