Case fan not spinning

[StubbleyBeard]

Current fan setup:

2 Noctua NF-P12 (Radiator)
2 Fractal Design Case fans (hooked up to 3 pin fan controller)
2 Noctua NF-A14 Case fans each plugged into motherboard 4 pin connector

750W power supply (I need 500, enough wattage to go with..)

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The problem is.. 1 Noctua NF-A14 which I recently added is not spinning, it's rather twitching. Like it's willing to spin every 2 seconds but it does not get that power to do so.

I've tried hooking them up to different 4 pin connectors but neither of that seems to work. I'm left with 1 Noctua NF-A14 spinning just fine, whilst the other is twitching. The fan it self is not defect.

Is this a motherboard problem?

 

[huilun02]

Possibly. Try using Speedfan to see if you can take control of your fans and make them work properly

http://www.almico.com/speedfan.php

 

[StubbleyBeard]

Sorry for my absence...

But I still did not manage to get the fan to work.
Controlling it with speedfan ain't working.

Question and situation still remains written in my first post.
Anyone got a solution?

 

[Paperdoc]

First of all, these are 3-pin fans connected to a 4-pin mobo port. Under normal circumstances, this means they will always run at full speed, whereas you say it does not run.

You say one NF-A14 works just fine, but the other just twitches no matter which 4-pin mobo port you connect it to. I assume that means that you have tried connecting it to the port that usually makes the first fan run perfectly. If that is the case, it appears the "bad" fan really is faulty. So why do you say it is not?

One thing to check: this type of fan comes equipped with two adapters designed to reduce its voltage so it will run slower and quieter. Do you have one of those in its power supply leads? Both of them? Try the fan with NEITHER of those adapters inserted into the leads.

The other thing to check is this. SOME mobo 4-pin fan ports can be set in BIOS Setup to behave as true 3-pin ports, which means they reduce voltage to reduce fan speed. Are any of your 4-pin ports set this way? I'm wondering if the fans are being fed a voltage so low they cannot start up.

 

[StubbleyBeard]

First of all, these are 3-pin fans connected to a 4-pin mobo port. Under normal circumstances, this means they will always run at full speed, whereas you say it does not run.

You say one NF-A14 works just fine, but the other just twitches no matter which 4-pin mobo port you connect it to. I assume that means that you have tried connecting it to the port that usually makes the first fan run perfectly. If that is the case, it appears the "bad" fan really is faulty. So why do you say it is not?

One thing to check: this type of fan comes equipped with two adapters designed to reduce its voltage so it will run slower and quieter. Do you have one of those in its power supply leads? Both of them? Try the fan with NEITHER of those adapters inserted into the leads.

The other thing to check is this. SOME mobo 4-pin fan ports can be set in BIOS Setup to behave as true 3-pin ports, which means they reduce voltage to reduce fan speed. Are any of your 4-pin ports set this way? I'm wondering if the fans are being fed a voltage so low they cannot start up.

Thank you for the response.

Whenever I post my desktop, all fans run perfectly fine. So judging by that, the fan is not faulthy. It just happens to occure that one of the Noctua Case fans stops spinning after a random amount of time and starts twitching, like it does not get enough voltage or power.

I did however connect them both to a low noise adapter. None of them are in power supply leads, they are connected as a bridge between the 4-pin connector on the mother board and the fan itself.

Ill try to run them without the low noise adapters, and have a look at the bios settings.

 

[Paperdoc]

OK, you have provided the explanation. These are 3-pin fans, and apparently the mobo's fan ports are acting like true 3-pin ports. That means that the way they reduce fan speed as necessary is to reduce the voltage supplied to them. BUT you inserted the "low-noise" adapters into each of their power supply lines. What that does is insert a resistor into the line, reducing the fan's voltage even further. Now, a 3-pin fan port knows a couple of important points about those fans. One is, the fan is very poor at starting up at low voltage. So the port always send full voltage to the fan at start-up. A few seconds later, when it has a chance to measure the actual temperature of the items being cooled, it reduces the fan's voltage (and hence speed) until the temperature is under control. From there on it adjusts the fan speed according to the measured temperature. The second thing is, it also knows that such a fan will stall if its supply voltage gets too low, and then the fan will have to wait until the mobo raises the voltage enough to start it up again. So the mobo will never reduce the fan's voltage below a minimum level, to avoid stalling the fan.

What you have done is reduce the voltage more than the mobo intends. So at some point when minimal cooling is needed, the mobo reduces the voltage to its minimum, but the low noise adapter reduces it much further, and the fan stalls. Then you never see it start up again, because the cooling required is not a lot and the voltage is not raised enough to start the fan.

You do not actually need the low noise adapters at all when you connect your fan to the mobo and let it control fan speed automatically. What the automatic control does is constantly measure the temperature at some sensors and adjust fan speed to keep just the right flow of cooling air to maintain the correct temperature. If you use the low noise adapter, what the mobo will do when it needs extra cooling is raise its voltage output enough to get the fan to provide correct cooling. If you leave the adapter out of the line, the result will be the same - the control system will set the fan speed to achieve the same amount of cooling, which means the fan will run at the same speed and be just as quiet. The difference without the low noise adapter is twofold: (a) at high temperatures requiring lots of cooling, the mobo will be able to speed up the fan to full speed if necessary, whereas the use of the adapter would prevent this; and, (b) at low temperatures the mobo can slow the fan down to its minimum speed without stalling it, whereas the use of the adapter causes stalling as you have seen.

Bottom line: remove those low noise adapters and let the mobo do its automatic control properly. It will do a better job of cooling, and it will not cause you any more noise.

FYI, why did the manufacturer supply those low noise adapters? They are intended for use when you connect the fan directly to the full 12 VDC from a PSU output for which there is no automatic speed control. Then you can use the adapter to reduce fan speed and cooling according to your own judgement.

 

[Paperdoc]

Thanks for the "best solution".

 

[StubbleyBeard]

And thank you for the outstanding explanation. I removed the low-noise adapters and I havem't noticed any fan twitches yet. So that's a good sign... Other than that I have no idea why Noctua included these low-noise adapters as a 'bridge' type, which is not directly connected to the full 12 VDC of the psu. I guess situation differs and it's dependant on the fan setup, in which you'd have to find a proper way to use the adapters without anything disfunctioning.

 

[Paperdoc]

Well yes. One related use for the adapters is trying to connect a 3-pin fan to a 4-pin mobo port. In that situation the mobo cannot control the fan's speed because the port supplies a fixed 12 VDC on the power lines and sends out the PWM signal for the fan to use to adjust speed. However, a 3-pin fan cannot use that signal and does not even get it - the PWM signal is on Pin #4 - so this is similar to connecting it to a PSU fixed-voltage output. So the user could employ the low-noise adapter to set a 3-pin fan on a 4-pin port to run at a fixed speed less than full speed. But in this case the mobo would be able to sense and display the fan motor speed via the signal on Pin #3.