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PWM - doing it wrong?

post #1 of 11
Thread Starter 
I'll try to keep this succinct - I've got some 4-wire PWM fans I'd like to make use of. They're 2.5A Deltas so I can't run them directly from my mobo (MSI Z77A-G45).

So, I figured I'd connect 12v and GND to the PSU via molex and run the PWM and RPM sensor wires to the motherboard header to get around the problem. Unfortunately this is not working. I can still vary the speed of the CPU PWM fan at will but the other units just run full speed. Now, SpeedFan is detecting the RPMs from the Deltas, so that's a positive, but it isn't doing a thing to regulate them. Ditto in the BIOS.

Is there something simple I'm screwing up?
post #2 of 11
its PMW dude
post #3 of 11
It's PWM as in Pulse Width Modulation. I have no idea about MSI bios but if you can manually adjust speed by using Speedfan then you can also make it automatic by creating a fan profile under Configure>Fan control tab.
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post #4 of 11
Quote:
Originally Posted by toolio20 View Post

I'll try to keep this succinct - I've got some 4-wire PWM fans I'd like to make use of. They're 2.5A Deltas so I can't run them directly from my mobo (MSI Z77A-G45).

So, I figured I'd connect 12v and GND to the PSU via molex and run the PWM and RPM sensor wires to the motherboard header to get around the problem. Unfortunately this is not working. I can still vary the speed of the CPU PWM fan at will but the other units just run full speed. Now, SpeedFan is detecting the RPMs from the Deltas, so that's a positive, but it isn't doing a thing to regulate them. Ditto in the BIOS.

Is there something simple I'm screwing up?
Not sure what the problem is. First let's rule out a couple of possibilities:
*Are the Deltas spinning full speed? Because that's what they should be doing if the PWM is not working.
*Are you sure your mobo is controlling CPU fan with PWM control and not voltage control?
post #5 of 11
Thread Starter 
Quote:
Originally Posted by doyll View Post

Not sure what the problem is. First let's rule out a couple of possibilities:
*Are the Deltas spinning full speed? Because that's what they should be doing if the PWM is not working.
*Are you sure your mobo is controlling CPU fan with PWM control and not voltage control?
Hey, thanks for the reply!

The Deltas are spinning full speed - both SpeedFan and the BIOS are tracking the RPMs (6000 lol) but no matter what settings I try with either interface the speed just won't budge.

I have absolutely no idea how the onboard controller (Fintek f71889a) is doing it but regular 4-pin PWM fans have no problem being controlled when plugged into the headers.
post #6 of 11
Thing is a PWM 4 pin fan will work just like a 3 pin voltage control fan. smile.gif

Do you have a 3 pin fan you can try on the mobo and see if it really is using PWM control? Or use a volt meter and see if the power pin is putting out 12v?

Is it possible your PWM signal is not getting to the Deltas?

In fact are you sure the Deltas are PWM fans? Not saying they are not. Just trying to cover all possible reasons they are not working on PWM control.

What is the Delta model number?
post #7 of 11
Thread Starter 
Quote:
Originally Posted by doyll View Post

Thing is a PWM 4 pin fan will work just like a 3 pin voltage control fan. smile.gif

Do you have a 3 pin fan you can try on the mobo and see if it really is using PWM control? Or use a volt meter and see if the power pin is putting out 12v?

Is it possible your PWM signal is not getting to the Deltas?

In fact are you sure the Deltas are PWM fans? Not saying they are not. Just trying to cover all possible reasons they are not working on PWM control.

What is the Delta model number?
Ok, turns out the PWM signal is definitely not getting to the Deltas.

Apparently something significant happened at some point because the only PWM header that's functioning correctly is CPU1, the other ones don't do diddly for modulation...actually, they aren't even fully powering the lowly test fans connected to them, which I couldn't've noticed since I had the Deltas pulling juice straight from the PSU.

Crapola - anyone know if they make a pwm-based fan controller? Voltage control won't work with the raging beast that is the Delta AFC0912DE - if it doesn't get 12v it stops dead in its tracks. Anyway, thanks for the assistance doyll!
post #8 of 11
Manual of your MSI board actually shows that cpu fan header uses PWM control, Sys fan headers 1 & 2 are 4-pin headers but they don't output PWM signal :
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post #9 of 11
What mm67 said.

Many motherboard 4 pin fan plugs are not PWM just like above.

So the Deltas are working PWM or what?

Delta fans are often wired differently so just because they have 4 wires into a fan plug does not necessarily mean they are PWM fans. That's why I asked for the model number so I could check. wink.gif
post #10 of 11
Thread Starter 
Quote:
Originally Posted by mm67 View Post

Manual of your MSI board actually shows that cpu fan header uses PWM control, Sys fan headers 1 & 2 are 4-pin headers but they don't output PWM signal :
Well no sheeeeeeeeeeeeeeeeet...I just got RTFM'd! Srsly though, thanks for clarifying the root issue, not the best of news but very helpful indeed yessir.gif
Quote:
Originally Posted by doyll View Post

What mm67 said.

Many motherboard 4 pin fan plugs are not PWM just like above.

So the Deltas are working PWM or what?

Delta fans are often wired differently so just because they have 4 wires into a fan plug does not necessarily mean they are PWM fans. That's why I asked for the model number so I could check. wink.gif
Oh, the Deltas are fine - definitely PWM, plugged appropriate wires into the CPU header and SpeedFan was able to do it's thing just fine thumb.gif I'm tracking the funky Delta wiring - I think it's mostly prevalent among their Dell OEM fans but regardless I always try to check the spec sheet on their site before I go messing with them.

And speaking of which I'm glad I still have all my digits, damn things are bloody dangerous. Thanks again for the help, guys - very much obliged!
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