PWM to 3-pin?

[Ttaskmaster]

Heya,

Quick question - Can I cut the 4th wire off a PWM fan and end up with a normal 3-pin voltage-controlled fan?

[aidanjt]

There's no need, the PWM connector is backwards compatible with 3 pin headers. All they did was add a PWM signal wire to the existing 3 pin design.

[Ttaskmaster]

No no... these are 4-pin fans on 4-pin headers.
I wish to disable PWM and have purely voltage-controlled fans.

[aidanjt]

No no... these are 4-pin fans on 4-pin headers.
I wish to disable PWM and have purely voltage-controlled fans.

If you want to disable PWM, then disable PWM in the fan control settings on your motherboard's BIOS settings. Everything I've seen so far supports that if you really want to do it that way. But to answer your question, yes, if your motherboard is uniquely retarded and doesn't let you disable PWM, cutting the PWM signal wire on the fan will make the fan default to running constantly at whatever voltage it's supplied with, it'd have to to be backwards compatible with 3 pin headers.

[Agent]

I wouldn't cut it - get a pin and push the metal tab in on the 4 pin socket. The cable will pull out. Stick a bit of electrical tape around it and you'll be able to reconnect it in the future.

[Pob255]

I wouldn't cut it - get a pin and push the metal tab in on the 4 pin socket. The cable will pull out. Stick a bit of electrical tape around it and you'll be able to reconnect it in the future.

This. the next question is why? there's good reasons for using PWM over voltage control.
Some fan motors will develop noise when reducing the voltage.
minimum start voltage vs minimum running voltage, most fans once they are spinning can be kept spinning at between 4-5v, however to overcome the friction and inertia to start turning from a dead stop you often need 5v or more. PWM does not suffer from this.
Larger range, most PWM fan controllers support a minimum speed below that of an equivalent 5v because of the minimum starting voltage issue with voltage regulation.

[Ttaskmaster]

This. the next question is why? there's good reasons for using PWM over voltage control.

I really don't know - It's not my system.
Something about how the CPU in a friend's w/c loop governing temperatures and not ramping the PWM fans up enough when the GPU is going sky high...

[herulach]

I really don't know - It's not my system.
Something about how the CPU in a friend's w/c loop governing temperatures and not ramping the PWM fans up enough when the GPU is going sky high...

That won't change with a move to voltage control, although it may mask the issue by setting the minimum speed to around 40% rather than 20%. A better solution would be just to one or more of the rad fans (or all the fans on one rad as I will am doing in the build I'm presently undertaking) from the GPU header, you need a £2 converter cable for the smaller socket, and to be on the safe side an adaptor which takes 12v from a molex/sata. I'm using one of these http://www.aquatuning.co.uk/air-cool...ga-pwm-adapter and one of these http://www.aquatuning.co.uk/air-cool...plitter?c=2810 to drive the fans on a 360 rad based off the GPU, the other 360 rad is controlled by the motherboard. This has the advantage that (because my gpus support it) I can actually power down the fans on one rad at idle or in solely CPU intensive tasks.

[Pob255]

Ahh I see now, is that a loop for the cpu & gpu or are there two separate loops?
or is it that the rad fans are the extraction fans and the gpu is air cooled?

if the cpu is water cooled and the gpu is not then you'd not want to move the fan control off the cpu to the gpu

if it's a single loop with both cpu and gpu then which ever is last is where you want the temperature monitoring, so you could keep the cpu header as the monitoring header if you put the gpu before the cpu in the loop or use an adaptor to move the monitoring to the gpu

Only thing I don't much like about herulach's setup is the phobya splitter, because I've got a rather low opinion of their products, I'd probably go for this swiftech one instead http://www.aquatuning.co.uk/cables/f...plitter?c=2810

[herulach]

Ahh I see now, is that a loop for the cpu & gpu or are there two separate loops?
or is it that the rad fans are the extraction fans and the gpu is air cooled?

if the cpu is water cooled and the gpu is not then you'd not want to move the fan control off the cpu to the gpu

if it's a single loop with both cpu and gpu then which ever is last is where you want the temperature monitoring, so you could keep the cpu header as the monitoring header if you put the gpu before the cpu in the loop or use an adaptor to move the monitoring to the gpu

Only thing I don't much like about herulach's setup is the phobya splitter, because I've got a rather low opinion of their products, I'd probably go for this swiftech one instead http://www.aquatuning.co.uk/cables/f...plitter?c=2810

It hasn't actually arrived yet, but it was just a general idea about what kind of thing is available. I've previously used cable based adaptors from Scan that do the same thing. TBH I'd be surprised if a GPU header couldn't stand 3 fans directly but that should certainly make cable management easier.

Bit OT but I've generally found Phobya stuff to be half way decent for the price, my experience is limited to stuff it'd be pretty hard to balls up though (extension cables, odds and ends of WC fittings)

[Ttaskmaster]

if it's a single loop with both cpu and gpu then which ever is last is where you want the temperature monitoring, so you could keep the cpu header as the monitoring header if you put the gpu before the cpu in the loop or use an adaptor to move the monitoring to the gpu

Yes, it's a single loop with 3 rads and I believe he runs it Res->240Rad->CPU->120Rad->GPU->200mmRad->Res.

That won't change with a move to voltage control, although it may mask the issue by setting the minimum speed to around 40% rather than 20%.

I would have thought some kind of fan curve/profile would be best, but he doesn't really want software control either.
He's got twin 140s off the main CPU and secondary CPU headers, with the others on a fan controller.

A better solution would be just to one or more of the rad fans from the GPU header

Ooh, good point - He's obviously not using them with water blocks on those cards!
I wouldn't have thought to do that...

This has the advantage that (because my gpus support it) I can actually power down the fans on one rad at idle or in solely CPU intensive tasks.

Interesting... How do you power them down?
Software control, like the MSI app?

[Pob255]

Yes, it's a single loop with 3 rads and I believe he runs it Res->240Rad->CPU->120Rad->GPU->200mmRad->Res.


I would have thought some kind of fan curve/profile would be best, but he doesn't really want software control either.
He's got twin 140s off the main CPU and secondary CPU headers, with the others on a fan controller.

Umm are the 140's on the rad? or are they case fans?
Sounds like the rad fans are on a fan contoller, I'm guessing a manual type, then having the 140mm case fans on pwm or voltage regulation isn't going to have much effect on the gpu temperature, it's the fans on the rads that need to be looked at first.
It could be a flow issue, not enough flow too keep the gpu cool under load because of so many steps/rads.
Or not enough heat is being dumped between the cpu and gpu by the 120rad so the warm water going into the gpu is effecting the temperatures.

It's one of those situations (as often happens with water cooling) where he'd have to sit down and do some actual testing and methodical checking and changes to figure out what is going on and what needs to be done to fix it.

[Ttaskmaster]

Umm are the 140's on the rad? or are they case fans?

All fans are on Rads.

In flow order:
- Reservoir
- 280 XSPC Rad with twin Corsair AF140s
- CPU water block
- 120 XSPC Rad with single Corsair SP120
- SLI 780Ti water block
- 200mm XSPC Rad with twin CoolerMaster 200 MegaFlow in push-pull
- Reservoir

Sounds like the rad fans are on a fan contoller, I'm guessing a manual type,

Almost - The CPU Rad has both fans on the Mobo CPU headers.

I don't think there's much of an actual problem, per se. He's just being a finicky, fussy git!
I can understand this, as I get the same way about my own temps, but I'm all air-cooled, with just an H100 on my CPU.

He's using a fan controller as he hates the constant up/down whine of PWMs spinning and doesn't want to mess about with software. he also likes to go completely silent and an FC makes it easy.

For some reason, he wasn't running the CPU fans off the FC, although I did correct that last night!

[aidanjt]

He's using a fan controller as he hates the constant up/down whine of PWMs spinning and doesn't want to mess about with software. he also likes to go completely silent and an FC makes it easy.

For some reason, he wasn't running the CPU fans off the FC, although I did correct that last night!

Your friend is very strange. Does he not realise that PWM fans only spin up proportionately in response to the thermal it's linked to? Manual fan tinkering will inevitably run higher than what the cooling loop *needs* to stay cool. If he wants a quieter fan profile, or link certain fans to certain thermal points, then his motherboard will almost certainly support that in the UEFI setup unless it's cheap junk. No Windows software fiddling required.

[Ttaskmaster]

I think he means to say that he only wants to hear that up-whine when he's overclocking/benchmarking and not all the time... and when he's OC/BMing, the fans are always on full chat anyway.
Certainly whenever I've gone round, his rig has been whisper-quiet and cucumber-cool during normal use.

[Pob255]

Well that depends on the motherboard, many these days just have a few pre-set profiles in the BIOS, usually a motherboard utility will allow you to set a custom profile up in windows.

Other than that, the corsair AF fans are not the best on rads, AP's are the ones designed for restricted air flow, also I seem to remember reading that there's a slight issue with the corsair fans and rads, due to the round frames they don't seal cleanly against the rad so there's a gap around the edge that lets air escape, so someone used duck tape around the fans to create a seal which improved the results.
It's not really an issue just that the corsair fans don't run as well as they could on rads.

swapping the 280rad and the 120rad might improve the gpu temps, but like I said you'd need to do some testing.