# Simple SATA/PWM question - everybody is telling me something different, what is correct?!



## Emiliano85 (Jan 17, 2020)

Hi guys.

I'm new to building, and am just about to finish up my first rig. I'm using the Asus Crosshair VIII Hero, with the Ryzen 3950x.

My board has 9 headers meant for AIO/waterpump/fans in total - 5 of these are dedicated for fans: CPU_FAN, CHA_FAN1, CHA_FAN2, CHA_FAN3 and finally H_AMP. All are 1amp, minus the H_AMP which is 3amp.

I plan to use CHA_FAN3 with a SATA powered three-way 4-pin (both motherboard and fans end of cable) PWM splitter (not to be confused with a controller just to clarify my question), connecting 3 Noctua 0.15amp fans to it.

And yes i know individual fan control off one single header will not be possible, and that i have to be carefull not to overload one single header with too many fans (which is not the case here anyway = 0.45amp of fans into 1amp header).

So to my question, which nobody seems to be able to give me a straigh forward answer to is:

*When SATA power is at play (specifically in a splitter - we are NOT TALKING about controllers) is it then overriding PWM control in every usecase?*

Simple as that. One person tells me yes, SATA will always run fans at full speed, regardless of having a 4-pin connection between mobo. and fans in the same loop - while others tell me it's perfectly working - what else would the 4-pin cable going into the mobo. in that splitter be for?

So which one is it? There are so many much more complicated things out there in regards of building and hardware, you can quickly learn by Googling/asking people questions, but this one above, seems to be some kind of Bermuda Triangle when one try to get more knowledge.....


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## JackCarver (Jan 17, 2020)

A SATA powered pwm splitter...the only pwm splitter I know looks like this:






Why do you need a SATA plug? Can you post a picture of your splitter?

Edit:
I searched for pwm-splitter at CaseKing, they were all like that one I posted above.


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## londiste (Jan 17, 2020)

SATA (or Molex) may be necessary for running 3 or more fans from one header. Depending on fans, motherboard etc but that is usually when headers start running out of juice.
Given a proper splitter, PWM signal will come from motherboard via the 4-pin connector and SATA connection will only provide power.


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## Emiliano85 (Jan 17, 2020)

JackCarver said:


> A SATA powered pwm splitter...the only pwm splitter I know looks like this:
> 
> View attachment 142481
> 
> Why do you need a SATA plug? Can you post a picture of your splitter?



So there is no definite answer to whether SATA+PWM works not in splitter cables?

I don't really need it, as the mobo. header provides enough power for the 3 fans as per my initial description. This type of splitter just happens to be the easiest one to get hold of (another thing that baffles me is how hard it is to find a normal 3-way PWM splitter without having to wait 5 years to order off Chinatown.net) where i am living unfortunately. I would prefer a non powered basic 3 way 4-pin PWM splitter, but at the same time i want to finish up my build now - it's just sitting and waiting for the last couple of bits. That's why i want to know, if this type will be okay for me - PWM is ofcourse a must, but since it's SATA powered, and people are telling me all sorts of stuff, i really don't know what to do from here....

This is the cable:


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## JackCarver (Jan 17, 2020)

3 fans shouldn't be a problem to run directly at the MB. The pwm signal turns the power supply of the fan on and of and so you can control the fan speed.
If you plug the fans to a SATA controller I mean that they would run at full speed. The additional SATA connection I only know from Fan controllers.


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## Emiliano85 (Jan 17, 2020)

londiste said:


> SATA (or Molex) may be necessary for running 3 or more fans from one header. Depending on fans, motherboard etc but that is usually when headers start running out of juice.
> Given a proper splitter, PWM signal will come from motherboard via the 4-pin connector and SATA connection will only provide power.



So in other words, you are saying it IS POSSIBLE to have SATA power and still have PWM when in the same splitter/cable loop?


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## newtekie1 (Jan 17, 2020)

The answer is a little complex, because it is going to depend on the splitter.

Some splitters just have a dummy pin for the 4th pin, so PWM is disabled and the fans will run at full speed.  I've only ever seen this on the super cheap splitters.

However, with other splitters, the PWM controller will work.

The splitter you just posted looks like it will work and the fans will be controller by PWM.


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## JackCarver (Jan 17, 2020)

Don't use the SATA connection, only use the pwm connection to MB, that's my advice and it should be sufficient in your case



Emiliano85 said:


> So in other words, you are saying it IS POSSIBLE to have SATA power and still have PWM when in the same splitter/cable loop?



No don't do so, only use PWM. You don't need that SATA plug.


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## Emiliano85 (Jan 17, 2020)

newtekie1 said:


> However, with other splitters, the PWM controller will work.



This i am aware of, problem is i can't get one easily. 2-way seems easy enough, but it's like 3-ways are illegal or somwthing, when you look at how hard they are to come about from a reputable webshop with quick delivery. Are nobody using these or how come?


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## londiste (Jan 17, 2020)

Emiliano85 said:


> This i am aware of, problem is i can't get one easily. 2-way seems easy enough, but it's like 3-ways are illegal or somwthing, when you look at how hard they are to come about from a reputable webshop with quick delivery. Are nobody using these or how come?


Power. An average fan header on motherboard can feed two or three fans. Splitter for 3 fans is likely enough not to work properly so they will not take that chance. Yes, enthusiast high-end motherboards can feed 3-4 fans without issue, sometimes more but it is not that relevant here as splitter can be used on any header and there is too large a chance to fail.

The splitter in your post will work. The 4-pin plug that goes to motherboard header will carry PWM signal and fan speed while molex will provide power.


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## JackCarver (Jan 17, 2020)

A midrange MB can feed 3 fans as I used 3 fans on one pwm header on my Z370 MSI gaming carbon


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## Emiliano85 (Jan 17, 2020)

JackCarver said:


> Don't use the SATA connection, only use the pwm connection to MB, that's my advice and it should be sufficient in your case
> 
> 
> 
> No don't do so, only use PWM. You don't need that SATA plug.



I appreciate your answer, and intention of trying to help - but this is exactly what i refer to in regards of mixed answers.

Using the splitter without the SATA connected was also my initial thought, but the question has become an obsession for me by now, as i can't believe it's so hard to find a definite answer. I want to learn as much as i can, as i really really started liking the game of building rigs, and might end up in a situation where i actually wanted to utilize all 5 ends on that splitter - in order to power 5 fans off one header (not that it would be a smart move) thus overloading it (if not for that SATA power). This time it's no problem, as 0.45 of total amps is fine on a 1amp header without additional power. But 5 fans would be another thing.

That's why i really want to know if this thing works, and if there is such thing as SATA+PWM working together or not.


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## Deleted member 193706 (Jan 17, 2020)

That's a molex connector isn't it, to power the fans if you don't have a spare fan header unless my eyes are mistaking me


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## newtekie1 (Jan 17, 2020)

Emiliano85 said:


> This i am aware of, problem is i can't get one easily. 2-way seems easy enough, but it's like 3-ways are illegal or somwthing, when you look at how hard they are to come about from a reputable webshop with quick delivery. Are nobody using these or how come?



I think it is because the PWM circuit struggles with more fans.  That is why PWM hubs exist.






						Amazon.com: SilverStone Technology Silverstone 8-Port PWM Fan Hub/Splitter for 4-Pin & 3-Pin Fans in Black SST-CPF04-USA (Newest Version): Computers & Accessories
					

Amazon.com: SilverStone Technology Silverstone 8-Port PWM Fan Hub/Splitter for 4-Pin & 3-Pin Fans in Black SST-CPF04-USA (Newest Version): Computers & Accessories



					smile.amazon.com


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## JackCarver (Jan 17, 2020)

If you want to use 5 fans or even more, then really buy a fan controller, as it's the best solution.

In your case, you can use the SATA plug to power the fans, but then they run at full speed, independent if you use also the pwm plug. If you want to control your fans speed then only use the PWM plug


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## londiste (Jan 17, 2020)

JackCarver said:


> A midrange MB can feed 3 fans as I used 3 fans on one pwm header on my Z370 MSI gaming carbon


180€ motherboard is not midrange.



Emiliano85 said:


> i can't believe it's so hard to find a definite answer.


The answer is simple for specific products. And you outlined the answer in your first post. Look at the motherboard specifications for the fan header - in your case most headers power up to 1A/12W (AMP and W_PUMP headers 3A/36W). With each fan consuming up to 0.13A you should be fine power 7 of these fans from one header (but I would still not recommend doing so). The same does not hold true for all fans - Noctua's fans are quite power efficient.

A simple example if a bit extreme fan choice to the other end - say you want to use a Noctua's industialPPC-3000 fan. That one has 0.55A in spec and it would be OK to run only one of these on one header.

External power source (usually a SATA or Molex connector) on the splitter immediately sidesteps this issue.


JackCarver said:


> In your case, you can use the SATA plug to power the fans, but then they run at full speed, independent if you use also the pwm plug. If you want to control your fans speed then only use the PWM plug


If SATA plug powers the fans but both speed sensor and PWM control is connected to the motherboard, fan speed is still controlled by motherboard, achieving exactly what he needs. The splitter in post #4 does exactly that.


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## Emiliano85 (Jan 17, 2020)

JackCarver said:


> If you want to use 5 fans or even more, then really buy a fan controller, as it's the best solution.
> 
> In your case, you can use the SATA plug to power the fans, but then they run at full speed, independent if you use also the pwm plug. If you want to control your fans speed then only use the PWM plug



Okay thanks.

But then my next question is: What is the purpose if such product (not that i expect you to know :-D)?

If it has SATA, it's meant to be used i guess - but it then renders the other part of the product (PWM) useless - then why put these two things together --> or more importantly why does this kind of product even exist.


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## JackCarver (Jan 17, 2020)

It‘s an either or....either you use the SATA plug or the pwm. For example if you have no free pwm at the MB then use SATA

But not together


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## TheLostSwede (Jan 17, 2020)

Ok, first of all, what you posted a picture of, has a Molex connector, not a SATA power connector. That part is to provide extra power to the fans.
The other end is for the PWM function and obviously connects to a fan header.
The question that springs to mind is this, are you connecting more than nine fans to your system (I only see eight PWM fan headers though)? Since as long as you're not connecting more than that many fans, why do you need a splitter? I used to run three fans off of a splitter, no extra power, so it works just fine.
However, there are slight variances between fans and having them all on a splitter, means you can't adjust them individually if there's one that creates a bit of fan whine.
If anything, I'd just connect a splitter without the extra power to the high amperage connector, as that would give you plenty power for the fans. I guess Asus is a bit silly with their pump connectors and don't allow them to be controlled.



JackCarver said:


> It‘s an either or....either you use the SATA plug or the pwm. For example if you have no free pwm at the MB then use SATA
> 
> But not together


Did you not see the picture the OP posted? There are cables where you get power from Molex or SATA, but there's still a header that connectors to the board fan header for PWM of all the connected fans.


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## londiste (Jan 17, 2020)

JackCarver said:


> It‘s an either or....either you use the SATA plug or the pwm. For example if you have no free pwm at the MB then use SATA
> But not together


No it isn't.
4-pin fan header pinout is: ground, 12V, RPM signal and PWM signal.
SATA (or Molex) is used in these splitters for ground and 12V while 4-pin that connects to motherboard runs RPM and PWM signals.


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## Deleted member 193706 (Jan 17, 2020)

londiste said:


> No it isn't.
> 4-pin fan header pinout is: ground, 12V, RPM signal and PWM signal.
> SATA (or Molex) is used in these splitters for ground and 12V while 4-pin that connects to motherboard runs RPM and PWM signals.


He didn't say they had the same function just that you use one or the other tbh it's been said 4-5 times in different ways by different people already and the op is still asking the same question 

Edit :ignore the first part I misread your comment although are you sure there is no ground and 12v in the pwm connector on these splitters and there's a 12v molex option if you don't have a spare header, like some fans give you both options


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## Emiliano85 (Jan 17, 2020)

r9370 said:


> He didn't say they had the same function just that you use one or the other tbh it's been said 4-5 times in different ways by different people already and the op is still asking the same question
> 
> Edit :ignore the first part I misread your comment although are you sure there is no ground and 12v in the pwm connector on these splitters and there's a 12v molex option if you don't have a spare header, like some fans give you both options


Please forgive me for not having the Divine fan knowledge (and reading skills) as you my good Lord....



TheLostSwede said:


> Ok, first of all, what you posted a picture of, has a Molex connector, not a SATA power connector. That part is to provide extra power to the fans.
> The other end is for the PWM function and obviously connects to a fan header.
> The question that springs to mind is this, are you connecting more than nine fans to your system (I only see eight PWM fan headers though)? Since as long as you're not connecting more than that many fans, why do you need a splitter? I used to run three fans off of a splitter, no extra power, so it works just fine.
> However, there are slight variances between fans and having them all on a splitter, means you can't adjust them individually if there's one that creates a bit of fan whine.
> ...


Because the remaining headers are placed in a way that will result in unnecessary cable clutter. And I plan to run them at the same rpm anyway. So a splitter would be a win win for me.


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## TheLostSwede (Jan 17, 2020)

Emiliano85 said:


> Because the headers have been placed in a way that will result in unnecessary cable clutter. And I plan to run them at the same rpm anyway. So a splitter would be a win win for me.



You need to learn how to route cables


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## Deleted member 193706 (Jan 17, 2020)

Emiliano85 said:


> Please forgive me for not having the Divine fan knowledge (and reading skills) as you my good Lord....
> 
> 
> Because the remaining headers are placed in a way that will result in unnecessary cable clutter. And I plan to run them at the same rpm anyway. So a splitter would be a win win for me.


You come here asking how a fan splitter works then throw sarcasm at me? I'm out gfl with your thread


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## TheMadDutchDude (Jan 17, 2020)

It's real simple. Not sure why everyone is complicating this so much!

SATA, or Molex, is there to provide the power only. Nothing more, nothing less. The 4th pin, for PWM, will still allow the fan to operate under normal PWM circumstances. You just need to make sure that you get one with PWM capability, most of which will say very clearly in the description of the item.

Jeez, oh man...


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## JackCarver (Jan 17, 2020)

If you connect your fans to a 12V Molex connection then they run at full speed. Where is the circuit which controls the power on/off in that case? That‘s in the mainboards PWM Controller, but it‘s connected to a constant 12V source of the PSU, so I say it‘s either or...


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## newtekie1 (Jan 17, 2020)

JackCarver said:


> It‘s an either or....either you use the SATA plug or the pwm. For example if you have no free pwm at the MB then use SATA
> 
> But not together



Yeah, that isn't how it works at all.

PWM still works if you plug in the SATA/Molex connector on the good splitters.



TheMadDutchDude said:


> It's real simple. Not sure why everyone is complicating this so much!
> 
> SATA, or Molex, is there to provide the power only. Nothing more, nothing less. The 4th pin, for PWM, will still allow the fan to operate under normal PWM circumstances. You just need to make sure that you get one with PWM capability, most of which will say very clearly in the description of the item.
> 
> Jeez, oh man...



Yes, exactly!  The SATA/Molex connector provides power to the fans.  PWM works independently of power going to the fans, in fact PWM fans always receive 12v(if it is a 12v fan).

You have to understand how PWM works.  A PWM fan is always receiving 12v. It doesn't matter if it is coming from a SATA connector or from the motherboard, the fan is always getting 12v.  The way PWM controls the fan speed is it pulses the ground.  Without a ground, no current will flow and the fan won't spin.  So how long the ground is pulsed controls how fast the fan spins.  The 12v source to the fan doesn't matter with PWM.

This is how PWM works:






If you set the PWM duty cycle for a 12v to 25%, like the last line in that picture.  Then the fan will receive a constant 12v from it's power source, but the PWM signal will only connect the ground 25% of the time, so current will only flow 25% of the time, and the fan will run at ~25% speed.  But when the ground is connected by the PWM controller, 12v is always flowing through the fan.


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## JackCarver (Jan 17, 2020)

PWM fans receive 12V with pulse width modulation, means 12V on/off all the time. That‘s the circuit which controls their speed. If you connect it to molex you have constant 12V means full speed the whole time and NO speed regulation. So keep that molex away if you want speed regulation.

Edit:
Fan controllers have also a molex connection to the PSU, but they have their own pwm Controller independent of the Mainboard. To connect the fans to a molex and to the pwm Connection of the mainboard makes so zero sense...


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## newtekie1 (Jan 17, 2020)

JackCarver said:


> PWM fans receive 12V with pulse width modulation, means 12V on/off all the time. That‘s the circuit which controls their speed. If you connect it to molex you have constant 12V means full speed the whole time and NO speed regulation. So keep that molex away if you want speed regulation.



Nope, PWM pulses the ground.  The fan motors are always connected to 12v, it's the ground that changes to adjust speed.  You can plug in the SATA/Molex and still have PWM control.  I know, I've got it connected that way right now.


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## JackCarver (Jan 17, 2020)

Ok you’re right. My pump has the same connections I remember. One molex and one pwm for Tacho and Speed. Didn‘t see it on fans till now


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## thesmokingman (Jan 17, 2020)

JackCarver said:


> PWM fans receive 12V with pulse width modulation, means 12V on/off all the time. That‘s the circuit which controls their speed. If you connect it to molex you have constant 12V means full speed the whole time and NO speed regulation. So keep that molex away if you want speed regulation.
> 
> Edit:
> Fan controllers have also a molex connection to the PSU, but they have their own pwm Controller independent of the Mainboard. To connect the fans to a molex and to the pwm Connection of the mainboard makes so zero sense...



You are wrong on all accounts.


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## JackCarver (Jan 17, 2020)

thesmokingman said:


> You are wrong on all accounts.



Yes that's true, really thought it switches between 12/0V which controls the speed.


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## TheMadDutchDude (Jan 17, 2020)

Are we SERIOUSLY still doing this? Bloody hell... honestly, you're just confusing the OP.

Yes, the fan will get the 12v constantly. However, the PWM controller resides within the fan to control this and will switch it on or off depending on the percentage requested.

It makes *ABSOLUTELY NO DIFFERENCE* if you get 12v from your motherboard, or 12v from your PSU. The PWM controller is on the fan itself and couldn't give two flying monkeys if it comes from your motherboard, your PSU, or your UFO in outer space.

I wonder why I bother sometimes...


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## JackCarver (Jan 17, 2020)

TheMadDutchDude said:


> Are we SERIOUSLY still doing this? Bloody hell... honestly, you're just confusing the OP.
> 
> Yes, the fan will get the 12v constantly. However, the PWM controller resides within the fan to control this and will switch it on or off depending on the percentage requested.
> 
> ...



Yes as some explanations out there in space are a bit misleading. And if you don't dive a little deeper, then you get it wrong:



> In short, *PWM* operates like a switch which constantly cycles on and off, thereby regulating the amount of power the *fan* or pump motor gains. The *PWM* system that is used for controlling *fans* and pumps *works* with the motor, either getting +12V (full power) or 0V (no power).



The fact, that there is a constant 12V but pulses the ground is not so clear in some explanations. So sorry for confusing the OP but I think if he reads his Thread then he get's it, as I too...

With the explanation above, you could mean there is a sort of voltage regulation within.


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## Emiliano85 (Jan 17, 2020)

Haha it almost ended up in another "this is correct, no this is correct, no 100% THIS is correct" discussion as always - luckily we got an answer.

Thanks @*londiste, @TheMadDutchDude & @newtekie1 for finely solving this enigma.*


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## TheMadDutchDude (Jan 17, 2020)

Honestly, you'd be fine connecting three Noctua fans to your one motherboard header without the need for the additional SATA power. They draw 0.15A each, bringing you to 0.45A under full load. Most motherboards in recent years can distribute 1A per header, which you're just under half of with that load.

I'm glad to have been able to give you an answer. I'm sorry for all the confusion caused by people not understanding how PWM splitters such as the one you showed actually work.


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## Emiliano85 (Jan 17, 2020)

TheMadDutchDude said:


> Honestly, you'd be fine connecting three Noctua fans to your one motherboard header without the need for the additional SATA power. They draw 0.15A each, bringing you to 0.45A under full load. Most motherboards in recent years can distribute 1A per header, which you're just under half of with that load.
> 
> I'm glad to have been able to give you an answer. I'm sorry for all the confusion caused by people not understanding how PWM splitters such as the one you showed actually work.


You’re a star! Really, i appreciate it - been looking for an answer for days. Unbelievable it had to be so hard.

I will go without plugin in the Molex, unless I manage to find a splitter without the power cable all together. Anyway nice to know how these things work regardless, might be I will not have the liberty to choose plan b in the future, which I am able to here by just utilizing the 4-pin parts of the cable as amps are lower than what header can provide.

Thanks again!


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## JackCarver (Jan 17, 2020)

Your plugs only have two connectors and I assume these are Tach and PWM, so sorry but you have to use the Molex then.
Otherwise they should have 4 connectors.


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## Emiliano85 (Jan 17, 2020)

JackCarver said:


> Your plugs only have two connectors and I assume these are Tach and Ground, so sorry but you have to use the Molex then.
> Otherwise they should have 4 connectors.


Yes, but really what I just wanted to know was quite simple and more of a general information: 

Will SATA always overrule PWM - deactivating the possibility to control fanspeed (when working with splitters - in general, not only this one).

Answer is no.


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## JackCarver (Jan 17, 2020)

Tach and PWM, sorry for that, I corrected it above. You said you will go without the molex but that's not possible, then buy a 4 pin PWM splitter.
The splitter I posted with picture will be the one without molex ;-)

Edit:
It's the same arrangement as with my pump. The pwm plug only has Tach and PWM signal, to get power I had to plug it with molex.


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