Hi everyone,
I just bought an Antec tricool 80mm LED fan today. I found that there is a 3-pin and a 4-pin molex connector on it. I know that the 3- pin goes to the MB, and the 4-pin to the power supply. The question is, Do I use both of them or only one? If so, which one? The cable from the fan goes to an adapter, which splits to wires (red and black) to the molex and one wire (white) to the 3-pin. 
Any help would be appreciated!

Thanks!

Do you have a link to the specific product or picture of it?
 
From your description, it sounds like the fan is a non-PWM style fan which is designed to be powered by a 4-pin molex power input.  The 3-pin connector on it with a single wire verifies this.  Given this assumption, the 3-pin connector does not need to be used.  You may plug this connector into an available motherboard fan header location though to monitor the fan speed.  I don't believe you will be able to adjust the fan speed via the motherboard fan header and BIOS, but only monitor what speed it is running.  But I don't know this for sure without intimate knowledge of the product.  A 3-pin fan header does not provide capability for fan speed adjustment since it assumes that the fan does not have necessary FET. The 3-pin fan header accepts tachometer input (sense), but does not provide a PWM fan output for fan speed adjustment.
  
It's safe to say at this point that regardless what the 3-pin fan header connection is for, it doesn't need to be used for the fan to operate.

3-speed switch lets you balance quiet performance with maximum cooling 3-pin and 4-pin power connectors provide convenient connections to your motherboard or power supply Fan-speed monitoring capability included (requires compatible motherboard)

 
Duh!
 
Since it is a 3-speed fan, the fan speed is controlled by a selector switch.  Of course.
 
If you power the fan via the 4-pin molex connector, the 3-pin fan header is only useful for monitoring fan speed through your motherboard if desired and is not required to be plugged in to a header if the feature is not desired.
 
So, there are three possible configurations you can use the fan in:
 
1) You can disconnect the 4-pin molex adapter and plug the fan directly into a motherboard 3-pin fan header in order for the motherboard to provide power to the fan and be able to monitor fan speed via the motherboard's BIOS.
2) You could plug in the 4-pin molex adapter and let your PSU power the fan directly if you have no available 3-pin motherboard connectors available and just leave the 3-pin fan header connection dangling free.
3) You could plug the fan into your PSU 4-pin molex AND plug the fan header into the board to allow the PSU to power the fan and the motherboard to read the fan speed.
 
The last option seems pointless though.  You might as well go with option one if you already have a 3-pin motherboard fan header available and want to monitor fan speed.

Thanks guys! I got everything working now. Just didn't want to plug in too much power to the fan. :-) I think I'll go with option one....since my horrible Trigem Motherboard has a three pin fan connector (that's right....a Trigem from an HP pavilion a335w.....from Wal*Mart............Maybe I should start saving money for a new computer build!)

rhussain

not a bad idea to go with option 3. Its generally a good idea to monitor fan speed if you're concerned about them failing. There's a bunch of possibilities a fan could fail (i.e. molex cable slipped off from tension, motor died, wear and tear on the cable, clogged with dust LOL). I've had antec fans like the tricool in 80m and 120mm with no issues for many years. But its a good idea to keep track of your fans in the event of failure you can have software alert you about the temps/etc. However, many people have clear side panels and they would be able to see if a fan is dead.

But option one also monitors fan speed.  That's the point; option one and three are identical except for three gets its power from the PSU and one gets its power through the motherboard.  Option three just adds more bulky wiring mess. 
 
In my diagram, the black wire is ground, the red wire is +12v, and the yellow wire is tachometer sense.  You see that one and three are identical except for the fact that option three splits the power and ground wire away from the tachometer sense.  There is no logical reason I can think of for doing this though since the 3-pin header that the yellow wire is plugged into is perfectly capable of also providing +12vdc and ground.

Thanks!  I think I should go with the motherboard and molex combo then since my motherboard is extremely old compared to the newer boards that the fans were made with. I guess I'll be drilling a few more holes to get the 80mm fan in a 85mm slot.......never thought of a 85mm fan???? Then again....it's in a HP too........