Case fan failing?

[Mantrid-Drone]

My 'newish' build desktop (i3 Gigabyte H87- HD3 8GB RAM) has worked near enough flawlessly for the first 9 months of its life. However earlier this week rather than the gentle hum of the case and CPU fans which, once the storage HDDs spin down and SSD is all that is being used, I heard something different.

It wasn't loud but it sounded like a fan motor had stuck or something was physically blocking the fan. I opened up the PC case and discovered that the two Akasa PWM 140mm Viper fans (one intake the other exhaust) were not spinning. They're powered from one fan header (Syst. 2) using an Akasa two way splitter cable (4 pin/3 pin).

No physical cause could be found so I checked the cable connections, shut the PC down and rebooted. The fans both spun up as normal and did so for the rest of the session. However the next day the same thing happened again, at some point those two fans stopped spinning.

The fans are 'guaranteed' for 50,000hrs and have had less than 500hrs use.

All the other fans (2 x 120mm intake, 2 x 120 CPU cooler and 1 x 120mm exhaust) operating from the other three 4 pin MB fan headers are running fine.

The PC should have plenty of power. The PSU (XFX 450W Bronze) can't be the culprit as it is very much over spec for the system even if it were being used at full whack. This problem appears to happen intermittently usually when the PC is doing little more than idling ie. it doesn't occur specifically when the system is under more stress.

If it were a power on that specific fan header issue you surely expect it to stop the fans completely but, as I said, from the sound of it when this happens the fans are trying to spin so they're certainly getting some power.

What might be the cause of this because the symptom don't make sense to me?

I don't understand enough about how PWM works to know if this is possible but I'm wondering if it is something to do with the PWM control of the 'master' 140mm fan of the pair. If that is cutting out both fans are stopped even though they're receiving power.

Does that make sense and if so would it be the 'master' 140mm fan that is causing this, a problem with the header itself or the MB PWM control of the header?

Advice appreciated.

 

[Paperdoc]

We need a bit more info to offer more precise suggestions:

1. Tell us exactly what mobo you have - maker and model.
2. Tell us which mobo headers you have plugged your fans into, particularly the pair that seem to misbehave.
3. Are you using any of the "low-noise adapters" that are inserted into the connector junctions of the fans in question?
4. In BIOS Setup, how are those mobo fan headers configured?
5. When the fans stall, if you leave everything running and open the case and give them a light push with a pencil or something, do they start up and keep running?

I agree this should not be happening, but there are a few factors that could cause it. The info requested above will help.

For your info, here's brief outline of how PWM fans work. The fan is supplied with power from connector pins 1 (Ground) and 2 (+12 VDC fixed). The fan generates a speed signal internally (2 pulses per revolution) that is sent back to the mobo on Pin #3. The mobo can display that speed, and monitor the signal for failure to turn, this generating an alarm if you let it - apparently you are not getting a fan failure alarm. However, the speed signal is NOT used to do actual control of the fan's speed. Control of the fan speed is accomplished using the PWM signal sent out on Pin #4. Inside the fan a small chip uses that to control the flow of current from the +12 VDC supply through the fan windings. It is a "% On" signal at about 25 kHz, and the higher the percentage of "On", the faster the motor can run.

A mobo header can accept only ONE speed pulse signal from fan(s) attached to it. Two or more signals at once causes huge confusion and misreadings. So any splitter (such as you are using) is missing its Pin #3 on all but one of its output arms, thus ensuring only one fan's speed pulses are sent to the mobo header. NEITHER of the fans is a "master" with any control over what the other does.

One advantage of a PWM fan us that it can run at slower minimum speeds that an older-style 3-pin fan under Voltage Control Mode, AND it can start up at a slower speed setting. A fan running under Voltage Control Mode needs a nearly full +12 VDC supply at start-up to be sure it does start, and then its voltage can be reduced. But is it still possible for a PWM fan to be fed a signal that is too slow so that it stalls and can't re-start.

There are many mobos now that use "fake" 4-pin headers, (and some with options you can set) that tend to work as "universal" fan headers. This makes use of a backwards compatibility feature of the new 4-pin fan design. The original intent was that, if you plug a 4-pin fan into a 3-pin header that uses Voltage Control Mode, it will still work just fine and it speed will be controlled by the mobo. You see, the older design does not supply a PWM signal (there is no Pin #4) and the 3-pin fans do not have any chip inside to use it, anyway. Control is done instead by varying the voltage supplied on Pin #2, from +12 VDC (max) down to about +5 VDC. If you plug a 4-pin PWM type fan into a mobo header operating this way, it gets no PWM signal to use, BUT the voltage being supplied is no longer a fixed +12 VDC. It varies, and the motor simply makes no attempt to modify that via its internal chip, because there is no PWM signal. Thus the motor behaves just like an older 3-pin fan. What many mobos now do is they use a header with 4 pins to make you feel good, but they basically do not use the 4th pin at all, and just use Voltage Control Mode (aka "DC Mode") no matter what fan you plug in, and it will work with either type of fan. Some mobos actually give you a choice in BIOS Setup to set a fan header to use PWM Mode, Voltage Control Mode, or automatically set itself according to what was plugged in.

Although these "universal" fan headers work with both fan types, there is a possibility that they could have a problem. One is that they do NOT work when you are using a Hub to connect 2 or more fans to a header because a Hub requires a PWM signal and all PWM-type fans. But that is not your situation - you are using a splitter, you say. The other is that it might send to the fans a Voltage that is so low that it allows the fan to stall. If the control system had been PWM, the fan might not stall because those fans are supposed to work at lower minimum speeds. But just maybe a too-low voltage could be sent out in Voltage Control Mode.

With the info requested up top, we can be more specific about your system.

 

[VirtualLarry]

There are many mobos now that use "fake" 4-pin headers, (and some with options you can set) that tend to work as "universal" fan headers. This makes use of a backwards compatibility feature of the new 4-pin fan design. The original intent was that, if you plug a 4-pin fan into a 3-pin header that uses Voltage Control Mode, it will still work just fine and it speed will be controlled by the mobo. You see, the older design does not supply a PWM signal (there is no Pin #4) and the 3-pin fans do not have any chip inside to use it, anyway. Control is done instead by varying the voltage supplied on Pin #2, from +12 VDC (max) down to about +5 VDC. If you plug a 4-pin PWM type fan into a mobo header operating this way, it gets no PWM signal to use, BUT the voltage being supplied is no longer a fixed +12 VDC. It varies, and the motor simply makes no attempt to modify that via its internal chip, because there is no PWM signal. Thus the motor behaves just like an older 3-pin fan. What many mobos now do is they use a header with 4 pins to make you feel good, but they basically do not use the 4th pin at all, and just use Voltage Control Mode (aka "DC Mode") no matter what fan you plug in, and it will work with either type of fan. Some mobos actually give you a choice in BIOS Setup to set a fan header to use PWM Mode, Voltage Control Mode, or automatically set itself according to what was plugged in.

I've heard that this is an issue with many cheaper Gigabyte motherboards. Probably the case here. I doubt that the fans have worn out already.

 

[JackMDS]

To be a real computer Enthusiasts it means to have additional hardware to be able to check for problems.

Thus get this and try the fans on Molex.

https://www.amazon.com/HDE-4-Pin-Molex-Replacement-Computer/dp/B0081K3ZS0

If it does not work you need new fans, If it works keep it on the Molex.

http://www.frozencpu.com/products/1...WM_Fan_w_Hydro_Dynamic_Bearings_AK-FN063.html

 

[Mantrid-Drone]

Thanks, particularly to Paperdoc for that extensive, interesting and helpful reply.

I did actually provide the info about the MB (Gigabyte H87-HD3) and the fan header being used (Syst.2).

On this MB the CPU fan header and three system fan headers are all four pin. I previously assumed the system ones were all PWM too but the manual shows the pinouts are the same except for pin 4. On the CPU fan header it is shown as "Speed Control" on all the other ones it is "VCC".

I'm still not sure of the exact meaning of VCC (Voltage Control Circuit or Current?) but I guess it is what Paperdoc describes as Voltage Control Mode ie. the voltage is varied from 12v down to control the fan speed.

I did understand already about the 4/3 pin fan splitter and was only calling the 140mm fan on the 4 pin connector 'master' for convenience. It is, I thought, the one whose speed was being controled by the PWM signal and the 'slave' identical 140mm fan on the 3 pin would necessarily run at the same speed.

Have I understood this correctly? If this was a true PWM header system the 'slave' on the 3 pin connector of the splitter would be getting the same pulsed voltage from the MB as the one on the 4 pin connector. Therefore, being PWM enabled as well, it runs at the same speed.

But in this case it isn't a true PWM header, just like the two other system fan headers it is VCC ie. voltage control. They are actually getting the same variable voltage, therefore run at the same speed and so I might as well have used non-PWM fans and splitter cable. The speed using VCC I assume is determined by the BIOS fan speed and/or temperature settings.

I've noticed there is an alternative fan pin header pinout system on my other Gigabyte MB a Z77- DS3H used in another desktop. The CPU fan header shows 1:GND, 2: +12v/Speed Control, 3: Sense, 4: Speed Control. The syst.1 fan header is the same for the first 3 pins but 4: Reserve (?). The syst.2 & 3 are the same as CPU fan header except 2: +12v ie. no Speed Control.

This means they are all PWM but why the differences in the pinouts, particularly for the syst. fan headers. It is confusing.

However understanding what is supposed to happen is one thing but it doesn't address the problem I was/am having.

Is the general consensus that this isn't a PWM (and actually can't be) the issue and that for an unknown reason the VCC is sometimes dropping voltage on my MB's syst.2 fan header so much that it stalls both the fans? Could a fault on just one of those fans stop both?

I really don't want to spend out on another 140mm fan but if one is faulty then I guess I have no option. Unfortunately they're out of warranty because I built the desktop over a period of two years as and when I could afford it. So even though 'new' they were out of warranty before I even used them.

Perversely since I noticed this problem I had the PC running for hours yesterday and again today and both fans are spinning away quite happily.

 

[Paperdoc]

Sorry, I missed the fact that the mobo specs were there already.

The labels for the three SYS_FAN headers mean that they ALL operate only in Voltage Control Mode just like a 3-pin fan header. That VCC label is a circuit term standing for "Voltage Common Collector", I believe, and it just refers to a specific point in a particular transistor circuit design. In practical terms, it means this header does NOT use PWM Mode to control its fans.

IF a header is using PWM Mode, it sends out the PWM signal to its fan on Pin #4. It is up to the fan to use that signal with its own internal chip to control the flow of current through its windings. The header actually knows nothing about how many fans are attached to it. If you use a Splitter, each fan gets exactly the same signals from the header and each separately applies the PWM signal to the power it receives.

But your mobo does not do this - it uses Voltage Control Mode instead. And again, the header does not know anything about splitters and multiple fans; it only sends out a varying voltage on Pin #2 to control the speed of its fan(s), and ALL the fans on a splitter receive exactly the same voltage. NEITHER fan is the "master" of the header, and the header does NOT change what it does in response to any fan signal. So for two fans attached to a header via a splitter, as you have, each of them receives the same voltage from the header, so both should act identically. And that is what these two fans are doing.

By the way, in reading the manual I realized why you have not been getting fan failure messages. By default, the BIOS is set NOT to send out those messages; you have to turn them on if you want them.

Now here's an interesting thought. All three of the SYS_FAN headers work exactly the same, applying the same control logic and using the same temperature sensor. So, ALL three headers should be sending out identical signals to their fans. (This does NOT apply to the CPU_FAN - it is done separately.) But you have some case fans that work, and one pair that do not. Try an experiment. Switch the splitter (and this fan pair) to another mobo header; maybe even interchange this pair with another fan set. If your problem is in the fans themselves, the pair that does not work as expected should still do the same things no matter which header they are plugged into.

Some mobos allow you to change a setting in BIOS Setup for each SYS_FAN header to set the minimum speed for the fans on the header. You can use this to ensure that the fan does NOT stall because of too little voltage. Your mobo manual does not show this an an option. On the other hand, it does indicate that you can make adjustments of many BIOS settings, including fan configuration, using the EasyTune utility included on the CD that came with the mobo. If you have not done this already, install that utility and run it under Windows. Look at the details of SYS_FAN settings to see if you can set a lower limit for fan speed on each SYS_FAN header If you can, raise the setting for the header that has those two fans on it.

 

[Mantrid-Drone]

Again very helpful reply. Like the first one I've made notes and copied the information/suggestions to my "PC Info and How to........" folder for future reference.

I'd already been into the BIOS to check the syst. fan settings. On this MB you can set each of the three headers separately to Normal, Silent, Manual (to use "Slope PWM" between 0.75 and 2.5 values/degree C) and Disabled.

I'd set it to Manual in the assumption that being 4 pin PWM fans they were using PWM ie. I didn't know at the time they were not - now I do. I wanted them running as quietly as possible but let the MB set the speed for temperature control priority rather than silence.

Whatever this problem was/is the last time this happened I took the sides of the case off to re-check the connectors yet again and tied in the fan cables + splitter + extension even more securely. They were very well supported anyway but I thought it best to over-engineer that just to rule it out as the cause.

I've been checking those two fans ever since and I've not had a repeat. But it still doesn't explain why it happened in the first place after 9 months using the same settings and the desktop hadn't been moved, let along jolted.

The MB is a bit odd in respect of the syst. fan problem warning options. You're right, by default, all warning options are disabled in the BIOS. But the problem is that MB doesn't have any built in speaker and I can't find any mention in the manual about any front LED flashing sequences/combo that would be used in the case of a fan failure.

Because of this one of the things I did when I built it was add a very simple mini-speaker to the MB as I like to hear that comforting single beep when the PC boots .

When this problem first came to my attention I switched the syst.2 fan header failure warning to Enabled to confirm the problem and indeed the two times it happened after that I had a constant and annoying tone from the speaker until I switched the PC off.

I disabled it again because of this and the fact I'd noticed the problem without needing the audio warning. Also :-

a). this really isn't a fan pair vital to temperature control in the case ie. they're probably overkill for anything I've used the PC for so far.

b). I have RealTemp in my system tray displaying the important CPU core temperatures (currently 21/21 degress C) so if there was any temperature problem I'd see it pretty quickly.

Anyway I'm going to stick with the current BIOS settings but continue monitoring this problem. If it recurs I'll switch the BIOS back Normal, see if that helps and if not then swap the fans/header connections around as suggested to see If I can identify the cause.

Thanks again for the advice given here.