Air Series SP120 PWM Quiet Edition not reporting RPM

Hello All,

 

A friend of me purchased the SP120 PWM QE fan and connected it to his mainboard as a CPU fan replacement, the fan worked however the bios reported n/a as the fan speed. When connecting a different fan the speed was reported. We then tested the fan on my motherboard and it also started spinning but again no speed was reported.

I then connected the fan to my lab powersupply and my oscilloscope with the tacho pin pull-up with a resistor (120kOhm) to 12V as described by the Intel 4-wire PWM fan specs (4-wire pwm fan specs.pdf) and the fan gave a square wave that looked good. When I compared this with the fan that did report its speed on the mainboard I saw no noticable difference, both fans looked fine.

So I grabed his mainboard (Asus M3A78-T)and my DMM in order to figure out how the mainboard measures the fan speed and found out the tacho pin is pulled up by a 2.7kOhm resistor to 5V not 12V. I then canged my test setup with those same values and now there appeared a noticable difference in both fan signals. The SP120 fans signal had an amplitude of only 3.5V and the lowest value was 1.5V, while the other fans signal had an amplitude of about 5V and the lowest value was just over 0V.

Apparently the Corsair SP120 fan tacho output has a too high series resistance to work correctly in this system. I do not know who is to blame here as Intels specs are unclear about tacho currents, resitances and detection voltages but is does seem strange that both mainboards have this problem with this fan while working with many different other fans, so I would guess the problem is in the Corsair fan.

In order to test out if this was really the problem I made an adapter with one resistor and one transistor and when I put that in between the motherboard and the SP120 fan the fan speed was detected corrrectly and everything worked smoothly. You can see the schematic of this adapter and the input circuit of the tacho pin on the mainboard in the picture below.

I guess the fan is not working properly and my friend should return it, I am however curious if more people have seen this problem.

http://kerrigan.student.utwente.nl/download/SP120PWM.jpg

Just received the replacement fan. Unfortunately it has the exact same problem.

(No RPM displayed, when connecting it to my adapter the RPM is working again)

 

Corsair is this a known problem?

Both fans have a unique number the first one 293913117521 and second one 296413117521

Maybe this helps finding out if there is problem with a specific batch.

 

It could be that most motherboards use much higher resistance pull-up resistors then both Asus mainboards (M3A78-T and Sabertooth 990FX) I checked with, and so these fans will work for them. I strongly doubt this however and I would expect more people with this problem.

hi there

i have just bought a dual pack of sp120 performace ed. and they dont report rpm on my asus sabertooth 990fx r2 in fact they dont report rpm in every mobo í've tested .. I am really disapointed with this.. and i also expected 4 pin conectors

Just tested the fans on an Intel desktopboard, no RPM displayed.

I'm gonna return the fans and buy a different brand. Which is very stupid as the fans seem solid and the problem could be solved by changing one resistor in the fan but as far as I know you cannot open the fan without damaging the sealing of the bearing.

 

Oh and moonlighter, if you had checked the corsair website you should have noticed all the 4 pin fans have PWM in their name, so all fans without PWM in the name are 3 pin fans. But I must admit the webpage with the fans is very messy. There should be a selection mechanism where you could select 3 or 4 pin and also twin packs do not deserve a separate entry in my opinion, the single and twin packs could be listed as variants under one fan type. These two changes would make the site much better.

I wonder if this is why one of my fans keeps losing it's RPM reading in the H80i, which then consequently spins up to full RPM because the controller thinks the fan has stalled.

i just received the Corsair Air Series SP120 (CO-9050014-WW) 120mm PWM High Performance Edition High Static Pressure Fan (Twin Pack) from newegg to use push/pull on my corsair h55 aio im also receiving 0 rpms from each fan i was using a y splitter and thought that could be the problem so i attached the h55 power supply directly to molex/psu and tested each fan connecter to the cpu fan and cpu opt header mixing and matching and no rpms are listed i plugged the h55 back in the cpu fan and its getting the rpms reported. i can adjust the speed of these 2 fans but not see rpms. also using sabertooth 990fx r2.0 board.

Hi! I also just purchased 2x the SP120 PWM QE fan (4-pin) , model nummber CO-9050011-ww

My Asus Motherboard (Sabertooth 990FX R2.0) do not read the rpm eighter. (same problem as above)

 

This looks like a consistant problem with the fan..

I was wondering: Is it the fan, or is it the motherboard? which one is to blame?? can I use the fan on a different motherboard? if so which ones are they confirmed to work with?

 

Also do anyone know of an adapter of some kind to manualy adjust the fan speed? I would have loved to build and adapter to get it working like mentioned in the first post, but sadly I don't have the tools.

Also do anyone know of an adapter of some kind to manualy adjust the fan speed? I would have loved to build and adapter to get it working like mentioned in the first post, but sadly I don't have the tools.

 

I'm using a Bitfenix Recon with the Phoebetria Software to control some spot fans in my system. It has been able to control every fan that I've thrown at it. The Recon is very inexpensive, and the Phoebetria Software can coexist with the Link Software without any mutual interference.

 

You also have temperature probes with the Recon that you can use to create custom curves for the fan speeds.

 

RodeoGeorge

I had the same problem, confirmed rpm does not work on 4 different sp120 hp fans on my motherboard's CPU fan header. Oddly enough rpm does work on the SYS fan header.

 

Soldering together the solution above makes the rpm work.

 

I also used some 0.001uf capacitors to fix the low rpm clicking noise these fans like to make.

 

My corsair keyboard K70 backlit keyboard had over 20 leds burn out after 3 weeks.

I ended up opening it up and just desoldering the led controller chip. It seems too much current is was allowed to the leds, so soon as a hot day came around leds would just start burning out.

 

So far every corsair product i've ever purchased has had some kinda design flaw that required soldering to fix.

I just found the same issue with my asus m3a78-em and a brand new SP120 QE

Bios also reports CPU fan not detected at boot.

RPMs not detected.

Not sure about this one but... PWM Fan control doesn't seem to be working but voltage fan control works.

I have a Sabertooth R2 and got exactly the sam problem!!! However my son has a Sabertooth R1 and does not have the problem. He has two SP120 PWM QE's running and has no problem. What is with theese newer boards that cannot handle 4 pins?

I have this same issue on a Sabertooth 990FX R1. I'm using two PWM fans on my Antec Kuhler H20 620 in a push/pull config with a PWR spliter connecting them to the MOBO. and was hoping to have the CPU fan header control the RPM based on the CPU temp. So I was very disappointed that the fan's aren't working. I am also using the same SP120 non PWM fans in the case as well (performance for exhaust and quite for intake). I wasn't worried about these fan's not reporting the RPM because I know they are working at full speed all the time regardless.

 

 

I have two questions for the original poster...

 

1 - If I make an adapter based on the schematic in the original post will it allow the MOBO to see the RPM and control the PWM fans?

 

2 - Is their any issue using the adapter between the power spliter and the MOBO header?

 

Thanks!

So the problem with SP120 PWMs not reporting RPM still unresolved? I've connected them with a Y-splitter directly to the front chassis header, it works but no RPM readings. :(