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  Fan Leds wont go on. 
 Date Written 
R G Jan 14, 2010, 08:45am EST Report Abuse

Recently ive bought a 20cm Fan which I hooked up to a 12V Adapter.
The problem is the leds wont go on and apparently I require a snipe case to use the leds.
Is there someway I can switch the Leds on manually and just keep em on?
I dont have a case to put in the little extra wires that came with the Fan cause its mounted on to a Laptop pad.


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kOrny Jan 14, 2010, 01:03pm EST Report Abuse
>> Re: Fan Leds wont go on.
I think fans with LEDs have 3 wires that you'd need to connect to the adapter somehow. 2 of them make the fan spin and the 3rd makes the fan light up. Only problem is that the adapter has 2 wires.

I dont know if this is your problem, but i think it should work if you can somehow connect that extra wire.

G. G. Jan 14, 2010, 03:26pm EST Report Abuse
>> Re: Fan Leds wont go on.
typical fan wires are either 2, 3, or 4. (unless they come customed wired for included fan controllers, speed settings, auto temp sense, or so forth)

2 = power (red) + ground (black)
3 = power (red) + ground (black) + rpm monitor (yellow)
4 = power (red) + ground (black) + rpm monitor (yellow) + PWM controlled (dont remember)

Please post a close up picture of your fan (backside showing the wires going up to the motor) + fan connector + the adapter you are trying to use.... I or we should be able to tell you if you what is going on with it.

by the way, did you say that the fan was running but the led are off?


john albrich Jan 15, 2010, 12:27am EST Report Abuse
>> Re: Fan Leds wont go on.
The PWM can be done with just the 2 power wires. If desired a 3rd wire can be added to provide RPM feedback to a motor controller. The colors of the wires can vary because there is no requirement/standard they have to follow. Some use yellow instead of white, I've seen some with Red/Blue/White, and I have an Antec that I bought just a year ago where all the wires are silver colored and it uses clear insulation...I suppose to look "cool"...they rely entirely on the connector polarization to safeguard everything.

The simplest fan configuration with LEDs can also have only 2 wires, and both the fan and LEDs are powered by connection to +12V and ground. It could be connected to a PWM driver as well, but the LEDs would begin to flicker as the fan speed is reduced from 100%.

Alternatively, you could have a 3 wire fan which provides 2 wires for the fan's PWM control + a separate wire that has to be connected to +12V (or +5V, depends on the manufacturer) for the LEDs so they get a constant DC voltage, and you could have a 4 wire fan for 2 wires for PWM control, 1 wire for RPM feedback, and 1 wire to provide constant DC to the LEDs.

edit to add:
Just realized one of my computers has a CPU cooling fan (labeled as an Intel fan) that has Black/Green/Yellow wires. Black=ground, Yellow=PWM control (a modulated +12V signal, or could be connected directly to +12V to run at max speed), and Green=RPM feedback.

R G Jan 15, 2010, 02:42am EST Report Abuse
>> Re: Fan Leds wont go on.
Hi everyone

Thanks for the replys.
it seems this fan has a Black+Yellow=Power 12V
and then there is a separate Black+Red wire and it looks like they go into the motherboard pins.
Im thinking of splicing the other wires into the Black+yellow with a 7V resistor or wouldnt that be necessary?

john albrich Jan 15, 2010, 05:42am EST Report Abuse
>> Re: Fan Leds wont go on.

When you say, "fan has a Black+Yellow=Power 12V"

Are you saying that this is a single wire AND it is colored either black with a yellow stripe...or yellow with a black stripe?

And, you think that wire connects to +12V? Is that from a label on the wire/assembly or some documentation that came with the assembly...or is it a guess?

Can you provide manufacturer and model number of the fan assembly? Point to a webpage about it? Provide a picture? The documentation?

I'd feel a LOT more comfortable with confirming things with more information. I definitely wouldn't do any splicing and absolutely no connecting to a motherboard without more info and/or separate testing. But, I'm leaning toward concluding you've got the configuration I described as
Alternatively, you could have a 3 wire fan which provides 2 wires for the fan's PWM control + a separate wire that has to be connected to +12V (or +5V, depends on the manufacturer) for the LEDs so they get a constant DC voltage
Note that a ground and direct +12V connection could replace the "PWM control" in that (effectively being equivalent to PWM operating at 100% duty cycle).

R G Jan 15, 2010, 08:55am EST Report Abuse
>> Re: Fan Leds wont go on.
hahaha yea sorry ou got a point there.

No what I meant was out of 4 wires in groups of 2.The Black and the "only Yellow" one =12V power.I know this cause its already hooked up to my 12V adapter.
The other 2 which isn't connected anywhere is another Black one and "only Red" one = I dont know"probably LED`s"

Heres the model on their website :

Please note that they say it doesn't support Led on/off but mine does....somehow.

john albrich Jan 16, 2010, 06:14pm EST Report Abuse
>> Re: Fan Leds wont go on.

Sorry for not getting back sooner...haven't been feeling well.

Based on the information at hand, and without being able to test it at home with my lab equipment, I can't tell you how to safely proceed with a 100% guaranty you wouldn't damage anything.

Without knowing more, my concern is that you could damage (or already have damaged) fan circuitry or the LEDs by simply applying voltages at random.

For maximum protection of the fan circuitry, my recommendation based on what I've been able to find is either get more info directly from CoolerMaster or find someone with that exact configuration of that model fan who can advise you.

I can only provide possibilities, not absolutes.

But, I'll give you what I've found.

Comparing your description of the wiring to what I've seen, things are even more confusing. ALL the specs I could locate on that fan say it is a "3-pin connector" fan, not 4-wire, and not even 3-wire. Although there is a suggestion from ONE reviewer that his fan had independent control of the LEDs...which suggests there may be more than one version of that model out there, and hence one version could be a 4-wire fan, OR you could have a fan that has been modified by someone in an attempt to provide independent control of the LEDs. But, I didn't find any explicit reference to a 4-wire version of that model.

Although they do provide a "standard" Berg 3-pin to Molex 4-pin adapter to get +12V and Ground from a standard 4-pin IDE disk drive power connector, and I'm pretty sure that's not what you're talking about. And since they do provide that adapter, that strongly suggests to me the LEDs are hard-wired to the +12V fan-motor power connector in that version of the model.

I point out the 3-pin berg to 4-pin molex adapter that comes with the 3-pin connector version of this fan ONLY brings out the ground and +12V connections from the 3-pin connector. The 3rd wire (IF it exists) is ignored.

The info I've gathered SUGGEST that the Red and Black wired connector is the fan motor power connector. That would SUGGEST that the Black and Yellow pair are the LED power wires. But that is by no means a sure thing, and it assumes this is NOT a user-modified fan.

With the exception of that ONE review, all reviewers in multiple locations I checked-out corroborated no ability to independently control the LEDs. That strongly suggests to me that in their 3-pin connector fan configuration, the LEDs are hard-wired into the +12V fan-motor power input line.

There is no explicit reference to that fan providing an RPM sense wire, regardless of the spec saying it has a 3-pin connector. However, manufacturer's often use 3-pin connector to denote an assumed RPM feedback capability. But unfortunately not all manufacturer's are consistent and I know that many case fans are listed as 3-pin connector but only provide 2 wires going to the connector...which of course means there is no standard RPM feedback connection. This is usually the situation with cheap case fans. The 3-pin connector is only to provide compatibility with the standard mobo 3-pin berg header, and it maintains voltage polarization of the connector to protect the fan circuitry. And, since I've seen this fan selling for $12, I'd have to put it in the "cheap" category...especially since it also uses a sleeve-bearing...the cheapest and most unreliable bearing possible.

There were suggestions this CoolerMaster fan is designed to run at a flat 700rpm 100% of the time especially considering it's a 19dB fan...extremely quiet even running full-out. Further, IF the LEDs are hard-wired into the fan motor's +12V line, then the manufacturer's generally seem to assume the fan will be running from a straight +12v feed, and not PWM speed controlled. However, that does NOT prevent a user from doing so, it's just not a typical mode of operation. If an RPM sense wire is provided, it might be used primarily to provide a fan-failure sense capability. There are even 3-pin to 4-pin molex connector that split out the RPM sense wire to a separate 3-pin connector to provide exactly that capability. The fan ALWAYS runs at full speed, but the RPM sensor provides ability to alarm if the fan stops rotating or for some reason starts to slow-down (e.g. bearing failure). See (note: viewing this may adjust the window size of your browser!)

But, as I said above, the adapter provided with the 3-pin connector version of this fan does not do that.

Specs show the fan has 2 DC current requirements. Unfortunately it again doesn't absolutely clear things up. That could suggest either the fan running at PWM controlled minimum and maximum speeds, OR it could indicate the fan running with and without the LEDs turned on, or a combination of both.

Both black wires are going almost certainly to be Ground. The fan motor-control circuit itself can take up to +12VDC so there is little danger of damaging the fan motor-control circuit by applying ground and then applying +12V to the red or the yellow wire to see what happens. But, the danger in doing so is you could damage the RPM feedback circuit (if it exists). Or the LEDs could be damaged IF they need an external current-limiting resistor (however that is somewhat unlikely).

Regardless, and I advise against this, IF you plan to go ahead and do more testing to determine if you have wires for separate LED power, then I would recommend using a 1000 ohm 1/2 Watt resistor in series with your power supply. I also suggest you limit the supply voltage to 6 volts. Any connections you make should be extremely brief, but should still dimly light the LEDs for that fraction of a second. And by "extremely brief" I mean like 1/10 of second or less. If you don't see LEDs light-up, then they are possibly already destroyed, or there is an internal break in the wiring of the LEDs, or there is no separate power input wire for the LEDs. (Note: with the resistor and reduced voltage, it is highly unlikely the fan blades will "tick" (move slightly) when you apply power to either the red or yellow wire)

edit to add:
comment about sleeve-bearing
moved a paragraph



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