Adding a case fan

[Odyssey]

I want to add a second fan for additional cooling. I have mounted the fan in the front of the case to bring air in from the front through a grill, but not sure how to do the wiring. It is a 12V fan with red and black lead with ends together in what looks like a motherboard jumper pair. Of course I can cut these off if they don't fit somewhere on the mobo.

What is the most convenient way to power the fan?

 

[G0AOZ]

Most modern mobos provide at least one pin header for a chassis fan. They are, however, usually 3-pin headers, the pins being all in a line with a plastic locator lug on one side. Looking down onto the motherboard with the pins forming a horizontal line and the locator lug below the pins, the connections will be as follows:-

Left pin (1) GROUND, Middle pin (2) +12v, right pin SENSE.

If you only have two wires, then ignore the SENSE pin. If your motherboard doesn't have a pin header as described above, you'll need to splice your fan wires onto an unused connection from the PSU. Remember that the normal colour code for PSU wires is BLACK for GROUND and YELLOW for +12v, and ensure that the splice is suitably insulated and tied back out of the way of fan blades etc.

ROGER - G0AOZ.

 

[Tarwn]

Another option: if it is a three pin connector you can generally order a cheap 3-pin to Molex adapter from most computer websites or stores. This saves you the trouble of splicing it yourself an allows you to connect the fan directly to a molex connector from the PSU.

-Tarwn

 

[Odyssey]

Goaoz, this 550 MHZ Slot 1 PIII mobo is 3 years old (or more), so don't known if it qualifies as "modern" , but not sure if I am finding a likely suspect. There is one set of jumpers (unused) on the mobo, sitting in quite a nice little white plastic "enclosure" between two of the AGP slots, and it is labeled "WOL"

There are also a couple of unused two pin jumpers (in a group which includes "reset", "HD_LED", "speaker", etc.) which are labeled "SMI" and "TURBO_LED" I assume the latter is definitely not the target, but might either SMI or WOL be the one in question?

There is an unused MOLEX from the ps, and another lead which looks like an (alternate) mobo connector (red, 2 orange, 2 black) terminating in a white mobo power type connector. I have no idea what this is for, but it is a replacement ps, so may have this as a provision for another type of mobo? This seems like a good candidate if orange is 12v+.

There is also a 4 pin square connector which has two black and two yellow leads and no idea what it is for either. But if yellow is 12v+, might this not be a good source leaving the (currently) unused MOLEX available for possible future use.

Tarwn, ordering such an adaptor might be a possibility. Must I use all three "inputs"? In other words, instead of connecting 3 wires from the fan to the adaptor, can I not disregard the 3rd element ("sense&quot and just connect the ground and power?

Thanks to both of you.

For anyone, am I likely to damage anything if I use a Voltmeter to check voltage and polarity of the above "possible leads", exercising due care, while the computer is switched on?

 

[G0AOZ]

I'd have expected a 3 year old mobo to possibly have an on-board connector for a case or chassis fan... The WOL is probably Wake On LAN - this is NOT suitable for powering your fan. Look on the mobo for a small white or brown plastic header, approximately 6mm x 8mm with 3 pins and a locating lug, as I described in my above post. This will be the ONLY type of mobo connection which is suitable for a power take-off for your case fan. Usually the CPU cooling fan will be connected to the motherboard - this connector will give you the pattern - check the board for similar connectors.

The other connectors you've described that emanate from the PSU will undoubtedly provide +12vdc. If they're not currently in use, there's no reason why you cannot connect one of them to power your fan, given that you have a suitable plug to fit. By all means check the voltages with a voltmeter - take the normal precautions as regards static, and ensure the meter test prods don't accidentally short any of the connections to ground etc.


ROGER - G0AOZ.

 

[Tarwn]

And yes, if you connect to a moles you can completely ignore the sense line, if you buy an adapter you will notice nothing connected to that pin, if you splice it yourself you will want to ignore it.

-Tarwn

 

[Odyssey]

Thanks to both of you for your help. bigsmile