how can I lower the fan speed

[EBH]

Hello

I am kind of a noob in electronics. I want to know how can I lower the speed on a fan that uses a 3pin molex (or isn't it called molex?) to get power from the mobo.

I want to get the voltage down from 12 to about 5-7 or something like this. Can i just cut one of the 3 wires (which?) and add a resistor? If so what value (how many ohms)? I don't think I need to complicate myself with a rheostat.

If it's really difficult i'll just coneect the 3 pin to a normal 4 pin molex and "hack" that to get 7V (or maybe even 5) as I've seen in a guide around here.

Thank you!

 

[Vio1]

you can get fan controllers already made to do the work for you.

 

[ancalime]

I am pretty sure you cannot volt mod a fan with a 3 pin connector unless you get a convertor like you mentioned.

A fan controller like the Sunbeam Rheobus is a cheap method as well.

 

[JamesXP]

Switch the red and yellows for 5v

 

[SolidxSnake]

Switch the red and yellows for 5v

It's a 3-pin connector, not a 4-pin Molex.

If you have a mobo that supports fan control, you can use software to change the fan speed. SpeedFan supports many mobo's fan headers by software. Try it out.

 

[Spawn-Inc]

does it look like this?

or this

the first one is a 3 pin fan connector (not sure if there is any other name) and the second one is molex. if its the first one then it is most likely plugged directly into the motherboard and should be adjustable in bios or via a fan control program such as speedfan. if its molex you can do the 5-7v hack that you are referring to by changing the wires around, no resistor or rheostat is needed.

note: the 3 wires for the 3 pin connector are for power, 12v (most of the time black), natural (most of the time red) and a rpm or speed sensor (most of the time yellow).

 

[Automata]

note: the 3 wires for the 3 pin connector are for power, 12v (most of the time black), natural (most of the time red) and a rpm or speed sensor (most of the time yellow).

Black is ground bud

 

[SolidxSnake]

does it look like this?

or this

the first one is a 3 pin fan connector (not sure if there is any other name) and the second one is molex. if its the first one then it is most likely plugged directly into the motherboard and should be adjustable in bios or via a fan control program such as speedfan. if its molex you can do the 5-7v hack that you are referring to by changing the wires around, no resistor or rheostat is needed.

note: the 3 wires for the 3 pin connector are for power, 12v (most of the time black), natural (most of the time red) and a rpm or speed sensor (most of the time yellow).

Both of them are Molex connectors. Molex is a company that makes many various types of connectors (I believe every connector coming from the PSU is a Molex designed connector). Looks like I was wrong. The OP said he has a 3-pin connector, which requires software.

On a side, note, standard colors for a fan on a 3-pin wire is:

Black - COM (this is standard for generally all electronics, on a 3-pin this is the right pin looking into the connector)
Red - +12v (middle pin on the 3-pin)
Yellow - Tach Output (Left on a 3-pin)

Some manufacturers use different colors. For instance, Delta's fans use blue for the tach wire.

 

[EBH]

Thanks for all the quick and many answers.

I'll first try speedfan (we'll see which if any of the 6 fan ports on my mobo are suported as everest, for instance, doesn't show me the speed on the only fan thats plugged in - other than the cpu fan). If that doesn't work I'll use the molex adapter and the "hack".

LE: I just downloaded and installed the latest version of speedfan and dislike it (the readings are off and it kinda slows donw my comp). I will use the molex hack and thats that... I just feel bad that I have so many 3pin conectors on my mobo and have to connect the fan directly to my psu

LLE: Done the molex hack and it works well. Got a little scared at first as my fan wouldn't start at all at 5v (thought I did something wrong) but after I jump started (with my finger) it worked fine. I'll use the 7V though as 5v is too little for this fan.

another noob question: does it matter what cable I connect to the 12V and which to the 5V? (the ground or the "hot" - red - wire).
if I connect them the other way around does the fan spin the other way also?

Thanks again!

 

[vanibanez]

Actually I like to get most of the fans off of the motherboard if at all possible. Unless you need to monitor fan speed I think its better to go direct to the PSU with your fan connections. It relieves some of the current flow on your motherboard.

 

[Spawn-Inc]

ya, plus if you really need to know the rpm you can just plug in the rpm wire only i believe.

 

[SolidxSnake]

ya, plus if you really need to know the rpm you can just plug in the rpm wire only i believe.

Correct.

I too don't like to use Mobo fan headers. I use my Sunbeam Rheo for my fans (Well, I will be when I get my WC upgraded )