One fan going at full speed most of the time

[daniel-2]

For a while now my computer has been fanning itself very loudly. I thought it was dust build-up or something so I cleaned it out, even reapplied the thermal paste and all that. It's pretty compadre.

It didn't help. So I looked at the BIOS and found that it's actually just CHA1 (the rear fan on my setup). It runs at over 2000 RPM right from boot up, and stays at that speed most of the time; it very occasionally takes breaks so it's not all the time, but in those periods in often judders between high and low as though the CPU temp is fluctuating rapidly.

But the core temps are cool most of the time, as in low 20s°C. I don't have a dedicated GPU.

The fan is a SilverStone FM121. It has a simple knob controller, which I keep on the lowest setting. It says on the box that the speed range is 800–2400. If I turn the knob up, it does speed up to around 2400. But on the lowest setting it's still running above 2000. If I unplug the controller, it runs at full speed (2400).

Tried fan tuning in the BIOS, and it made no difference. CHA2 (at the front) remains pretty stable at about 850 or something, and the CPU fan runs around 1000 or something. They speed up normally when I'm doing an intensive task.

So right now it's unplugged. Any ideas on what may be causing this? I'd greatly appreciate any help!

 

[Vic 40]

Tried the fan on a different fan header? See if it is the fan or the motherboard.

Not to be rude,but if you suspect it is the fan why not buy a more silent one? Fans aren't that expensive.

 

[Paperdoc]

So you have a rear case fan that runs fast most of the time. Not realizing which fan, you first cleaned the CPU cooler. Now you cite the reasonable CPU temperature as a reason to expect this not to happen. What you've missed is that the two CHA_FAN ports that run the case ventilation are guided by a different temperature sensor that is built into the MOBO, not the one inside the CPU. So try looking for dust buildup on mobo components, particularly any that have a finned heatsink on them. That is the most likely location of the mobo temp sensor.

Check also the air intake dust filters (usually thin foam sheet) to make sure they are clean, and the exhaust area to make sure there is nothing blocking that area. I once had a problem because of a huge ball of cables for accessories plugged into the case at the back and blocking the exhaust vent.

 

[daniel-2]

Tried the fan on a different fan header? See if it is the fan or the motherboard.

Not to be rude,but if you suspect it is the fan why not buy a more silent one? Fans aren't that expensive.

That's a good idea. I think the board temperatures I'm posting below might be responsible though.

The noise is just a symptom. I'm okay with the fan being loud when it's running at full speed. It just doesn't need to be running at full speed all the time.

 

[daniel-2]

What you've missed is that the two CHA_FAN ports that run the case ventilation are guided by a different temperature sensor that is built into the MOBO, not the one inside the CPU. So try looking for dust buildup on mobo components, particularly any that have a finned heatsink on them. That is the most likely location of the mobo temp sensor.

I cleaned the whole box. Everything on the motherboard looks clean, and there are no major obstructions. When I'd finished, the only thing I wasn't happy with was the PSU which has a little bit of dust in it that I have no way of getting to without voiding the warranty.

I had no idea that the chassis fans ran off a different sensor. I'm sort of wondering why both of them aren't running at full speed then...? But I think you have found the problem...

According to HWMonitor:
TZ00: 28°C
TZ01: 30°C
SYSTIN: 115°C
CPUTIN: 28°C
Mainboard: 115°C
CPU 28°C
Core: 28°C (highest value of four)
Package: 29°C
Utilizations: 5% (highest value of four)
Hard drive air flows: 26 and 30°C

According to SpeedFan:
System: 115°C
CPU: 28°C
AUXTIN0: 29°C
AUXTIN1: 109°C
AUXTIN2: 106°C
AUXTIN3: 108°C
HD0: 26°C
HD1: 29°C
Temp1: 28°C

Fan speeds at this time:
CPU Fan: 1300RPM
CHA1 Fan: Disabled
CHA2 Fan: 900RPM

According to the BIOS page, the motherboard's temperature is 29°C.

EDIT: My motherboard model is ASUS H97M-E. There's a topside photo of it here. I'm a noob when it comes to this stuff. The PCH heatsink is apparently that golden disk thing. And the VRM doesn't have a heatsink...? I don't do any overclocking. Are those the parts that are supposedly getting hot?

 

[daniel-2]

This isn't solved. I think I must've accidentally marked this as solved.

I'm getting readings of 115°C from my motherboard. Googling shows up a few threads from people with the same problem, but there doesn't seem to be a solid answer.

 

[Paperdoc]

I presume HWMonitor is a third-party software utility for monitoring these things. NOTE that its temperature readout for your mobo is VASTLY different from what you mobo says in BIOS Setup. I have seen this before, and the usual explanation is that the third-party software needs to be calibrated for the specific mobo you are using it on, but that has not been done. VERY likely the HWMonitor readings are wrong.

Now, how does that relate to your fan speed? IF you have HWMonitor somehow taking control of the fan via the CHA1 mobo port, that faulty reading certainly would have it force that fan to full speed. If you were to find the correct way to calibrate it, that might solve your problem. Otherwise, try un-installing HWMonitor.

Still, I am intrigued to realize your post says that this fan comes with its own controller (a knob and pot on a bracket) and when you set it very low the fan still runs at 2000 rpm. Very weird! First, where does that fan's power come from - is it plugged into one of the mobo CHA_FAN ports, or into an output directly from the PSU? If it is plugged into one of the mobo CH_FAN ports, go into BUIOS Setup and check that port's configuration. See your mobo manual, p. 2-14. It indicates that each of those two ports can be set to CD Mode or PWM Mode. I'm pretty sure your rear fan is a 3-pin type that con ONLY be controlled in DC Mode, so you MUST set that mode for the fan port it is connected to. After you chage that, be sure to SAVE and EXIT. If you do that, the mobo should be able to control that rear fan's speed. THEN, to ensure that it can do that properly, set your fan's own manual control knob to its max so that it does not interfere with the voltage the mobo is supplying. See if that gets the rear fan under control.

 

[daniel-2]

Thanks Paperdoc.

I only installed HWMonitor and SpeedFan after you told me about the chassis fans running off the motherboard sensor. I am thinking they are wrong too, because I feel as though 115°C would probably make itself known... and that PCH heatsink is not hot to the touch.

The fan has two cables. One plugs into the PSU, and the other (yes, a 3-pin type) plugs into the motherboard, currently the CHA_FAN1 port. It evidently draws power directly from the PSU since it stops when I unplug that cable. It was set to PWM mode before, but I've changed it to DC mode now. ...And no difference.

 

[Paperdoc]

OK, I finally found some info on this fan and understand its design. It cannot be controlled by a mobo CHA_FAN port at all. It gets is power solely from a Molex output of the PSU (at a fixed 12 VDC). It reports its speed to a mobo CHA_FAN port via its 3-pin female fan connector, but ONLY the speed line (Yellow to Pin #3 of the connector) exists. To control its speed you MUST connect its included speed control module to the fan via a cable that plugs into a 2-pin custom connector on the fan chassis. The only way to make this fan controllable by a mobo 3-pin CHA_FAN port (cannot be done for a 4-pin PWM Mode port) would be to make some custom wiring changes, and I don't recommend that if you don't understand them.

So, the only control of this fan's speed is by the knob on its own controller module. The fact that this control no longer does its job tells me the controller module itself is faulty. The variable resistor in it is not covering the full range of resistance it was designed to do, and hence the fan's voltage is not being reduced enough when the knob is set to low speed. You need a replacement of this unit, or at least of the pot in it. No amount of adjustment of BIOS Settings or HWMonitor can do this fix.

 

[daniel-2]

Perfect! That's really good to hear because I was half expecting it to be some kind of problem with the mobo. And replacing that would really suck. A fan is easy. I don't think I'll get that model again if you're saying that the speed can't be controlled by the motherboard like all my other fans. There was a time when the knob controller worked perfectly, but really I'd prefer the temperature sensors take care of it.

Thank you so much, Paperdoc! My sincerest gratitude to you for taking the time to look into this for me. The mechanics of these things is something I don't know anything about.

 

[Paperdoc]

Yes, replacing the fan entirely with the RIGHT type is your best solution. Both of your CHA_FAN ports on the mobo are true 4-pin ports that operate in PWM Mode. So for sure you should buy only a 4-pin type of fan (NOT 3-pin). Your old fan is the common 120mm size, so stick to that size for easy replacement.

When you get your new fan installed it will have only ONE set of wires (4) coming from it ending in a female 4-pin fan connector with 4 holes. It only plugs into one of your two CHA_FAN ports - does not matter which one. It will not connect to a PSU Molex output. When you get it installed, on first boot go immediately into BIOS Setup and to where the fan ports are configured. Make sure the CHA_FAN ports are set to the PWM Mode, not DC Mode, and set for automatic control of the fan. If you have to change any setting there, remember to SAVE and EXIT.