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Tim the Toolman

Registered
Joined
Apr 20, 2001
Still a newbie to OCn never used fans in my cases til now... Can someone evplain instalation of different types of fans.....

1. fans with no connector red/black wire only
2. difference between 3pin and 4 pin fan.....
3 Does y spliter fan12v also...?
4. does it matter which way you plug the pin connection in the fan into the mobo no specs that I can see on mobo or manual...
 

Shadow ÒÓ

Mod in Hiding
Joined
Dec 20, 2000
Location
Pensacola, Florida USA
Tim the Toolman (Apr 25, 2001 04:23 p.m.):
Still a newbie to OCn never used fans in my cases til now... Can someone evplain instalation of different types of fans.....

1. fans with no connector red/black wire only

Red is positive.....black is negative. Connect red to red, black to black.

2. difference between 3pin and 4 pin fan.....

3 pin fans have an rpm sensor....4 pin have rpm and thermal sensors

3 Does y spliter fan12v also...?

not sure I understand this one, but fans with y splitters come default to run at 12v

4. does it matter which way you plug the pin connection in the fan into the mobo no specs that I can see on mobo or manual...

since the fans are DC powered, yes polarization is an issue. If I'm not mistaken, reversing the polarization would cause the fan to run in reverse

Careful messing around with this.....I just blew up a P3V4X by accidentally crossing the leads at the board.
 

klosters64a

Senior Member
Joined
Dec 17, 2000
Location
Seattle, Wa
Fans with only red and black wires, but no connector are known as untailed fans. They're usually very inexpensive, but you must "tail" them yourself. You can build a Molex connector---these are the rectangular four wire connectors that hang from the power supply. They are keyed so that they get connected correctly--- that will plug into the "daisy chain" of Molex connectors. Or you can splice the two fan wires to the proper Molex wires.

It's MUCH better to buy or build a jumper connector so you DON'T splice into one of the PS's own set of three or four Molex connectors!

Important things to remember: Shadow OO's mention of ruining a motherboard is a very valid caveat.

While DC Voltages within PC's range from 1.5v to 12v, you gotta remember that there's plenty of Amperage behind those little voltage values. Think car battery. Obviously 700 Amps isn't a concern in PC's, but .5 Amps can kill you!

Assuming that we're talking about standard fans made for PC's, those fans run on 12 volts DC. However, the red wire from the fan does NOT plug into the red wire of a Molex connector. Why? Because Molex connectors have a yellow wire--this is the 12 volt supply. There is a black wire next to the yellow wire from Molex "city." This is the 12v yellow wire circuit's return to ground. The fan's red wire goes to the Molex yellow wire. The fan's black wire goes to the Molex black wire that is next to the yellow wire.

Looks like the Molex red wire is left out of the picture. It is, 'cause this is the PS's 5 volt line. The black wire next to the Molex red wire is the 5 volt circuit's return to ground. It's sometimes said that a ground is a ground is a ground. While this is often true, I like to keep my wires in a shipshape and Bristol fashion.

CPU fans generally have three wires. The standard red and black, plus a yellow or blue wire. If the CPU fan draws more than 2 Watts, it's better to plug it into the Molex chain. The little "3 to 4pin" adapters that have a Molex plug on the non fan end only have two pins. This is because the third yellow or blue wire from the fan can't be plugged into the Molex chain.

In the case of a CPU fan, the third yellow wire is a tachometer sensing lead that goes to one of the three-pin Fan Risers(along with the red and black wires) on the motherboard. AFAIK, if the CPU fan has a third blue wire(instead of a yellow) it's a sensor from the fan that simply relays if the fan is spinning--or not.

Delta 38 cfm CPU fans have a red, black and blue wire. The Delta should NEVER be plugged into one of the mainboard's 3-pin fan risers. In other words, just because some idiot sold you a 6 Watt case fan with a 3-pin connector on it doesn't mean that it's OK to plug it into the mainboard! When in doubt, go Molex.

The little 3-pin plug from the CPU fan is keyed to match up with the 3-pin mainboard fan risers. It's also fairly obvious how to plug this into a "3 to 4-pin" converter(two actual pins in the tiny plug on one end, 4-wire Molex plug on the other end), in order to tap into the Molex chain.
 

stool

Senior Member
Joined
Dec 20, 2000
Location
Albany, NY
Some fan manufacurers use the blue wire as an RPM sensor also. In some cases, the yellow third wire is a rotor alarm sensor, in other words, it lets you know if the fan stops spinning.
 
OP
T

Tim the Toolman

Registered
Joined
Apr 20, 2001
Thanks for all the info ... 2 more questions
1. Is it bad to have an A/C current fan near your computer...?
2. With going molex do you lose your sensors ?
 

asmodean

Senior Member
Joined
Mar 21, 2001
Location
Finland
I must correct one thing. Putting minus to plus & vice versa doesn't cause the fan to spin the wrong way, it doesn't spin at all. There's some electronics inside the fan to prevent wrong spinning direction. This is with the current fans, don't know about some older fans, tho.
 

Fro

Registered
Joined
Mar 14, 2001
definitely be sure your mobo can handle the draw. i blew the fan headers on my be6-II usign the delta that way like a retard :(
 

asmodean

Senior Member
Joined
Mar 21, 2001
Location
Finland
The 0.5A limit is propably all fan headers combined, so use your PSUs molex connectors for such a thing.
 

klosters64a

Senior Member
Joined
Dec 17, 2000
Location
Seattle, Wa
I think it's "gospel" to keep AC out of computer cases. If an AC powered fan is placed near an open PC case...frankly, I don't know for certain. Trying it shouldn't hurt anything.

Yes, when a CPU fan with a third yellow or blue wire is connected to a 3 to 4-pin Molex adapter, only the red and black wires from the fan are connected into the main power "daisy chain." Rpm sensing is lost. Don't worry, if you use a Delta 38 CPU fan, your ears will keep you updated in real time--there's no danger of not noticing that the Delta From Hell-a isn't spinning!
 

ken257

Senior Member
Joined
Dec 20, 2000
A while back I had 2 Radio Shack 120mm AC fans in the top of a full tower pulling air through a radiator and never had any probs. They were quite nice and very quiet.
 

Thelemac

Administratively Deficient
Joined
Mar 15, 2001
klosters64a (Apr 26, 2001 09:00 p.m.):
Don't worry, if you use a Delta 38 CPU fan, your ears will keep you updated in real time--there's no danger of not noticing that the Delta From Hell-a isn't spinning!

Especially when it stops cause you smashed it with a baseball bat!