PWM Help Please

Chimp Paradox · 19 Oct 2014 at 16:14

I have a Phantek fan hub, 3 Phantek PWM fans and I am using a Asrock Extreme 6 Z97.

Basically, I cannot get it to work. I can get a single fan to work if I plug it directly into the CPU fan header, though. I've set it up to run at 50% speed and it runs at 50%.

The moment I route the fans through the fan header they all run on 100% irrespective of the BIOS settings (which work with a single fan). Can anyone help? Seems very odd to me - something to do with the PWM part of the hub?

Tealc · 19 Oct 2014 at 18:56

You have linked the PWM hub back to the CPU fan header, right?

If so then maybe the hub is faulty or the lead has an open circuit on the PWM line.

If not then doh.

Chimp Paradox · 29 Oct 2014 at 15:44

Yes. Defo connected. I have spoke to Asrock to ensure no reported issue and they have confirmed in the negative. So I am going to RMA this and then report back...

Chimp Paradox · 5 Nov 2014 at 20:20

So I got the replacement and exactly the same issue!!! What the hell is going on? Any suggestion? Thanks!

Tealc · 5 Nov 2014 at 20:49

Just to be clear you RMA d the fan hub right? You mentioned asrock.

I wonder then if the tach signal is not coming back nicely and the pwm controller on the motherboard panics and sets pwm to 100%.

sjpt4x · 6 Nov 2014 at 16:45

Hi,

I'm running an ASRock Z87M OCF with Phanteks PWM hub (included with the case).

I'm not sure if this is the same issue I came across last night on my new ASRock board, and I haven't fully investigated it but try setting the fan speeds to something ridiculously low, like 1-5% and see if that lowers the fan speeds. It worked for me somewhat. I managed to get the CPU fan speed down to 1000RPM at 1% when at 50% the fans were almost running full blast (2600RPM - max is 2800RPM).

It could be that you are only meant to use 3-pin fans on the hub as opposed to PWM fans so the PWM hub may not be able to control them properly. I'm just guessing at this point though.

I will do some more testing tonight and report back with my findings.

Chimp Paradox · 7 Nov 2014 at 08:21

I am using Phantek PWM fans and Phantek hub.

I did RMA and this is the second one I am trying now.

Tealc · 7 Nov 2014 at 12:46

Does your CPU fan header report a tach speed when it is connected to the PWM Fan Hub and steaming along at 100% duty cycle?

Chimp Paradox · 8 Nov 2014 at 07:16

Yes, it reports 1200rpm. This goes down when connected directly also

Tealc · 8 Nov 2014 at 09:53

It's unlikely that both PWM fan hubs would be faulty so I'm not sure what the problem would be. I've never owned one of those PWM fan hubs but have built dozens of similar units and know how they work and provided one throws a logic level PWM signal into them they should spit out a more or less constant voltage depending on the input duty cycle.

Maybe your motherboard is not correctly set to PWM mode and is running a variable voltage control instead.

Maybe the PWM implementation on your motherboard is non Intel standard and therefore the PWM fan hub doesn't function as a result.