Sometimes takes a while for fans to turn on

Nebell

Nebell

2[H]4U
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Jul 20, 2015
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I have a weird issue.
Sometimes my computer fans take a while to get going. I have 11 fans in my system, right now 6 are spinning and 5 are just trying to spin - moving a bit and then just stopping.
In BIOS they are all set to manual (75% of rpm). They are all Thermaltake Riing 12 and have led lightning, those who don't spin at the beginning have a much weaker led light compared to the ones spinning.

While I was writing this, all of them started spinning, not at the same time but eventually. What would cause this? The temperature is quite low as I have a custom water build with 2x240 and 1x360 radiators and 11 fans, so maybe they are reacting to the temperature?. But since they are all set to manual, shouldn't they all fire off at the beginning?
 
Generally with fans there is a minimum voltage that they require to be able to spin. A reduction in voltage does not always translate to an equal reduction in speed (or at least it will until you cross the minimum threshold at which point you get a complete stop in motion). From what I have observed using manual fan controllers for fans and pumps, at some point the fan or pump will not be able to start and sustain motion. The LEDs are dim because they are drawing their power from the same connection the fan motor is. If you reduce voltage to the fan motor the LEDs are also going to receive a lower voltage.

If your BIOS is trying to control fan RPM and not simply the voltage supplied to the fan headers on your motherboard, then it is quite possible that it is supplying insufficient voltage to the fans. To be clear, the BIOS would try to control RPM by by increasing or decreasing fan voltage, but because it is trying to maintain a set RPM it will have to constantly adjust the voltage as it reads the fan's RPM, as opposed to you being able to set it to provide a constant 75% of max voltage or similar. As it adjusts voltage to the fan headers on the motherboard it sometimes drops below what the fans need to start spinning.


Oh and just to make sure, you didn't plug in the inline resistor extension cables that Thermaltake includes with those fans did you?
 
I think I did connect those cables. But it doesn't take long for the fans to start spinning. Eventually they all fire up.
 
Nebell said:
I think I did connect those cables. But it doesn't take long for the fans to start spinning. Eventually they all fire up.
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Then that is a big part of your problem. Those cables have resistors wired in to them to reduce the voltage that the fans receive which reduces their speed. Then you are telling the BIOS to adjust voltages to further reduce speed, so it is dropping voltages even further which is leading to insufficient voltage for the fans.

Either use only the resistor extensions or only the BIOS. If you take out the resistors you can set the BIOS to lower RPM% if you find the fans to be too loud. Thermaltake includes those cables for people who don't have fan controllers or built in ways of controlling voltages.
 
^^This, remove the resistors. They are only used when needed ie. when the fans are too loud and you can only reduce the speeds via the resistor add-on.
 
Not gonna happen :D
With 11 fans I have a lot of cables wired up all around the computer, and it's a custom hardline build so it would be too much hassle. They stay off for only a few minutes before kicking in.

But thanks for pointing out the problem, now I know what is causing it :)
 
Have you tried setting your fan speed in BIOS to 76% or 77%? A small increase in the setting may get your fans to start more reliably without an appreciable increase in noise.
 
RedWagnum said:
Have you tried setting your fan speed in BIOS to 76% or 77%? A small increase in the setting may get your fans to start more reliably without an appreciable increase in noise.
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I don't think I can. I only have a few choices. I can't increase by 1%, more like choose speed between 75%, 100%, 150% and 200%. Or maybe I have not looked close enough.

Koween said:
How many motherboard headers are you using for those 11 fans?
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4 if I can remember correctly. I have those Thermaltake connectors which can control 3 fans at once (they came with the fans). So I should have connected 4 of them.
 
Well as far as I know, most fans need something like 6-7V to start-up. Once they are spinning the voltage can be lowered a bit more. PWM fans seem to be able to start at even lower rpm/%, because they are getting the full 12V, but in pulses (also, some motherboards just run them at 100% for a very short time just to make sure they start). Now, if you have inline resistors and pwm control then that, as mentioned, makes it more difficult for the fans to start. Since you don't want to redo the wiring then, probably, the only thing left to do is to set up a higher speed in bios, so that they start spinning when your pc starts, and then autorun speedfan or something like that to lower the speed once windows boots.
 
Koween said:
... Since you don't want to redo the wiring then, probably, the only thing left to do is to set up a higher speed in bios, so that they start spinning when your pc starts, and then autorun speedfan or something like that to lower the speed once windows boots.
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I've used SpeedFan like forever. Since I am watercooled I have nothing connected to the CPU fan headers but I use SpeedFan to control some my other system fans. They are 120mm GT's (don't recall the model) 3 pin fans connected to the MB 4 pin connectors. The nice thing about SpeedFan is that it does just exactly that, IF you set it up properly. That means turning off fan control in BIOS, setting the headers to voltage control in SpeedFan, then setting your speed range. When the system boots up the fans start at 100% then once SpeedFan starts it will ramp the fans down to your desired speed. That may be another option for the OP if SpeedFan is compatible with his motherboard. Not sure if it works the same way with PWM fans since I don't have any but I would think it is similar.
 
RedWagnum said:
Not sure if it works the same way with PWM fans since I don't have any but I would think it is similar.
Click to expand...
yes it works exactly the same way. if op is interested in trying speedfan and I recommend you do, here is a good vid:

 
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