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Fan revs up then cuts off, then repeat.

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sorabishop

Registered
Joined
Feb 6, 2017
So I got this 6000 rpm fan with 4 pin connector for motherboard, I plug it in it'll go full speed but when I use speed fan app. To slow it down it'll slow down a lot then rev back to the percentage I set it at then cut out again. The fan is 12v 2.80amp.
 

notarat

Member
Joined
Nov 11, 2010
2.8Amps for a computer fan seems excessive to me. I don't think I've ever seen one with an amp rating that high that was meant for a consumer-grade computer
 
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sorabishop

Registered
Joined
Feb 6, 2017
I pulled from a bitcoin minor. This is the 2ND one the first one I put in didn't have a problem. It has no labels so I don't know sprcs
 

Johan45

Benching Team Leader Super Moderator
Joined
Dec 19, 2012
2.8 amps is likely higher than the rating on the fan header
 
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sorabishop

Registered
Joined
Feb 6, 2017
I should probably get a speed controller then for it.
I had emails the asrock company about the current ratting for the fan pins a few days ago
 

wagex

Chapstick Eating Premium Member
Joined
Jan 14, 2011
yeah its probably the motherboard cutting the power off to the fan header for overcurrent that's too much iirc fan headers are rated for 1 amp
 

Mandrake4565

Mr. Clean Senior Member
Joined
Jan 12, 2012
2.8 amps is likely higher than the rating on the fan header
Agreed

I should probably get a speed controller then for it.
I had emails the asrock company about the current ratting for the fan pins a few days ago
Most fan headers I've seen are rated at 1A. I'd definitely consider getting a fan controller. You could blow the header trying to run a fan that powerful on it.
 

NiHaoMike

dBa Member
Joined
Mar 1, 2013
Get an adapter to power the fan direct from the PSU but still let the motherboard control it.

2.8A is not that unusual for a high end PC. The one in my PC is 3.2A, although actual power usage is much lower under usual conditions.
 
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sorabishop

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Feb 6, 2017
My fan speed controller came in the mail today. the fan I'm using is a 4 pin and the controller is 3 pin only. I plugged it it barely went faster than my 1300rpm fan for some reason. Then I took the wire from the 4ft slot not being used by the controller and sliped it into the positive and it then went full speed.
 

trents

Senior Member
Joined
Dec 27, 2008
My fan speed controller came in the mail today. the fan I'm using is a 4 pin and the controller is 3 pin only. I plugged it it barely went faster than my 1300rpm fan for some reason. Then I took the wire from the 4ft slot not being used by the controller and sliped it into the positive and it then went full speed.

jerry rigging. We love it! Good move!
 
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sorabishop

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Feb 6, 2017
My speed controller is making my other delta fan rev up and power down then rev back up. I have tried different ways of wiring it to, any time it gets <30% fan speed.
What should I do to prevent this?
 

trents

Senior Member
Joined
Dec 27, 2008
It looks like your speed controller is analog instead of digital. Nothing wrong with that. Analog will give you more granularity of control but won't allow you to reduce the fan RPM as low as PWM control will.

I have three Dell/Delta 4000 120x38mm fans on my water cooler controlled by a 30 watt per channel Sunbeam controller. Very similar to your controller only yours is beefier with 45 watts per channel. You got a good one.

My delta fans had a custom four pin connector that was meant for connecting to the proprietary headers on a Dell server motherboard. So I had to replace the ends with standard 3 pin connectors in order to have them fit my controller's 3 pin connections. I took the three pin connectors from some old dead fans (or some very cheap ones) for this purpose. I just cut the wires about six inches up from the connectors, cut the old connectors from the Deltas and spliced the new connectors and their wires to the Dell fans using a soldering iron and some shrink tube. I had to do it this way because the little metal keeper clips on the ends of the Delta fan wires were a different style than normal.

Now here's the important part. I only used two of the four wires. That's all you need with a controller. You only need a power wire and a ground wire. I folded the unused wires back out of the way and secured them with the shrink tube.

Four wire/four pin fans have:

1. A power wire
2. A ground wire
3. A tach wire - this reads the RPM
4. A PWM wire - this is used by the motherboard to interrupt the power in pulses to manage the fan speed.

Typically, standard colors are used to signify which wire does what. So do some research and find out by color which two wires are the for power and ground on the fans. Then get some 3 pin fan connectors and insert the fan wires into the appropriate holes on the plastic connector. One of the holes in the plastic three pin connector will be for the tach wire but it will be a "dummy" because the controller does not use the tach wire.

Now I don't mean to insult you but I hope you realize that the Lamptron controller is powered directly from the PSU, not the motherboard and then the fans' speed is controlled directly by the rheostats on the Lamptron controller.
 
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sorabishop

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Feb 6, 2017
the 2 wires didnt work for me i have tried all kinds of wire configurations with this fan but cant get it to go below 4.86Volts <30% fan speed witch is 1800rpm from what it sounds like. im comparing to what i heard from when i used speed fan app.
in this picture is how i have the fan wired that i can get to maybe 2.60volts 8%-15% fan speed to 100% 6000rpm. i got the voltages with my multi meter
i would like to put the fan on my gpu heatsink, it said at 100% load this cooler can get 55C now with this fan im wanting to put on it i hope it can go as low as <50c. because i run it standing alone the metal gets very cooled.
i got both fans from an antminer s7 so i assume there both the same type. i assume because the working one is unlabeled. IMAG0170[1].jpg
 

trents

Senior Member
Joined
Dec 27, 2008
Okay, I see what the problem is now you were trying to address. Sorry, I misunderstood.

The fans you have chosen have a high impedence. Impedence is resistance to starting to turn (sorry, awkward wording. I just can't think of a better way to say it). It's like inertia. It takes a lot of voltage to start them turning but once that resistance is overcome they start to spin faster than you want. This cannot be managed by an analog fan speed controller very well because they still must supply whatever the voltage is that is the threshold to starting the blades to spin. It is just a part of how the fan is made. This is why fans that have PWM ability are so popular. PWM (pulse width modulation) breaks the electrical flow into pulsations but each pulsation has full voltage - enough to get the fan turning. The speed is controlled by controlling how long each pulsation lasts. So PWM overcomes the impedence issue and allows fans to be run at lower, quieter speed levels than analog control does. But PWM is more difficult to fine tune.

Either you need to get some fans with lower impedence or you need to get a custom made PWM controller that can handle higher fan amperage than the PWM built into motherboards can. There's a guy in the classified section of the forum who builds custom PWM controllers. You may also be able to buy after market ready made ones that are beefier. You can also build your own.
 
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sorabishop

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Feb 6, 2017
i blow up he fan . . . :-/ my 2nd strongest fan is .28 amps hope that does a better job at cooling the gpu than the .21A
thnkas everyone for the tips
 

demien88

Member
Joined
Dec 1, 2016
I have similar issue with front fan. I can hear it slow down and returning to max speed in random intervals. I think its connected to PSU directly since I had no need to plug it into motherboard when I changed it. Its 120mm fan that came with case probably some Chinese crap it says nothing on it. Is it possible that its going bad? Or its GPU not so sure
 
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trents

Senior Member
Joined
Dec 27, 2008
would this be able to control fans seperatly on the device or all at the same time?

No. All fans connected to this block would receive the same pulse with modulation from the mother board. If you have need for some fans to run faster than other then just get more than one of these blocks. They aren't expensive. Each block would then be connected to a different 4 pin header on the motherboard and controlled separately from bios. Of course, this assumes you have multiple 4 pin PWM headers on the motherboard. Or you could use a combination of the PWM block I referenced and the analog controller you have already installed to control different fans in the system. If some of the other fans are 3 pin you could run them off thje analog controller.