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Confused about 3 pin vs 4 pin fans, Molex connectors, PWM, etc etc.

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techiemon

Member
Joined
Jan 29, 2007
I am incredibly confused about 3 pin vs 4 pin vs PWM vs whatever when it comes to power consumption of fans. I am worried I am going to end up blowing my MB or causing other damage because I am not sure how or where to plug in the fans.

I had an installer do all the cabling and installation of components to my system, so the wiring is too tight and too organized to find where stuff leads.

I just had to change out my rear exhaust fan as it was leaking oil and making noise. Because of the above I just cut the wires and pulled everything through both directions. And what I found was that this case fan was a DC12V 0.4A fan, but the connector was Molex, not 3 or 4 pin. He had connected to a row of 4 Molex connectors. The fan was a case branded fan from FSP. Cheap garbage essentially... So I bought a Sickleflow 120 ARGB fan that says it is a 12VDC 0.15A fan. 4 Pin PWM. So... I cannot for the life of me find a 4 pin to IDE connector. I can find a 3 pin I think, but not four. So I ended up plugging this into an extra cable I saw laying around that connects to the CPU MB 4 pin connector. Note, I originally had a Cooler Master CPU dual fan heat sink, I pulled that out and put in a Noctura. But it is not plugged into the same place as the installer had plugged it in. I think the guy I asked to helped me yanked all that out and plugged it in to the AIO ports instead, he said it doesn't matter, same same... So right now it is plugged into a Y MB slot, but only one fan on the Y, so I would guess I am safe to do this and not to over do it for voltage on the MB. I have no idea why he had it in an Molex, as I read Molex seems to be less volts no? So maybe that is why the fan started dying? I am also looking for a ARGB extender, as the connection is at the front of the MB, and the connection to the new fan is way too short. But that's another issue, so for now, the fan is working but the LEDs are not as I haven't plugged it in yet.

Can someone shed some light on two things...
1. the differences between the Pins, PWM vs I forgot the other one, and the IDE voltage issues.
2. Anything I should know to avoid frying my MB or overdoing it?

Note, I did find a site http://www.playtool.com/pages/psuconnectors/connectors.html that sort of explains some of this, but I still kind of do not understand 100%.

This probably seems like a very novice question, but I have struggled with this more this time than in the past as I have 10 fans in my correct system right now as I am running WCG and GPU grids more than I was before and I need to keep the PC cool. And with all the wires and connectors and how the installer did things, it got confusing real fast. Note, I still have three FSP intake fans in the front, that problem I will end up replacing with better fans in the near future, and I am worried about the same issues as now, as everything seems to be plugged into Molex rather than MB power connectors. And finding a four pin to Molex connecting wire may be a bit hard.

Anyway, please help.
 
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EarthDog

Gulper Nozzle Co-Owner
Joined
Dec 15, 2008
Location
Buckeyes!
1. 3-pin is DC/voltage controlled and 4-pin is PWM. I have no idea what you're referencing when you say a third mode or ide (ide was an old interface for storage). Some motherboards 4-pins support both (see your manual)
2. Yes. Look at your manual to see how much each header supports power wise. If it doesn't say, assume 1A/12W.

You've been a member here for 13 years and paid someone e to build your system?!?!?!? :eek: :D
 

JLK03F150

What have I done! Member
Joined
May 17, 2005
Location
Georgia
Computer fans need two wires to work, +12v & Neutral (aka ground, earth).
The third wire on a 3 wire fan is the tachometer. Plugged into a motherboard, the tach will tell the motherboard the fan's rpm and the motherboard can vary the fan's speed by lowering the +12v to the fan.
The forth wire on a 4 wire fan is the PWM signal (third wire still a tach). Simply put, a PWM fan varies it's speed by pulsing voltage instead of lowering voltage.

What you are calling an IDE connector is called a Molex connector. The molex will only have 2 wires. If the fan is a 3 or 4 wire, there will be another fan header connector for the tach and/or PWM control.

I hope that helps a little.
 
OP
techiemon

techiemon

Member
Joined
Jan 29, 2007
1. 3-pin is DC/voltage controlled and 4-pin is PWM. I have no idea what you're referencing when you say a third mode or ide (ide was an old interface for storage). Some motherboards 4-pins support both (see your manual)
2. Yes. Look at your manual to see how much each header supports power wise. If it doesn't say, assume 1A/12W.

You've been a member here for 13 years and paid someone e to build your system?!?!?!? :eek: :D

Because I don't have time to build the system. I choose the components I want, through reading and asking on this board and then let someone install it all for me. They can do it a whole heck of a lot faster than I can, and I have no patience for small items and things like that, I am not 20 anymore either. haha.

IDE meaning Molex connector. I will go back later to edit that. My MB is all four pin, and my fan that I just installed in 4 pin. My question is why did the installer tie everything together with a molex strip of four fans? I thought the voltage for those fans is less? Also it seems that CPUID can still monitor the fan speeds even doing that, not sure.

Computer fans need two wires to work, +12v & Neutral (aka ground, earth).
The third wire on a 3 wire fan is the tachometer. Plugged into a motherboard, the tach will tell the motherboard the fan's rpm and the motherboard can vary the fan's speed by lowering the +12v to the fan.
The forth wire on a 4 wire fan is the PWM signal (third wire still a tach). Simply put, a PWM fan varies it's speed by pulsing voltage instead of lowering voltage.

What you are calling an IDE connector is called a Molex connector. The molex will only have 2 wires. If the fan is a 3 or 4 wire, there will be another fan header connector for the tach and/or PWM control.

I hope that helps a little.


so is it safe to say that how I plugged in that fan is right and safe? And yes, it was originally on a Molex strip of four.

Is it also safe to plug in more than one four pin 12v fan to one MB fan socket?
 

Ben333

Folding for Team 32!
Joined
Feb 18, 2007
Good catch JLK, I'm 100% the he is talking of the Molex plug, not IDE. (It's really an Amp connector, not Molex, if you want to get technical) You said almost everything I was going to say. Only thing I will add is, it is safe to put multiple fans on a MB fan header. Super high amp ones? No. But if they're .3 amps or less, you should be fine putting up to three on most headers. Check your board specs if you're looking to put more than two "normal" fans on a single header. 3 & 4 pin fan "Y Cable" spliters are a great way to power extra fans and retain speed control.

EDIT: You posted JUST before I wrote my above post ^

To answer your questions:
#1, the voltage is not less. 12V is the max from a MB header, and 12V is what you will get from the molex plug as-well. They also supply 5V, but it is unlikely that you had the fans wired for that. So MB vs molex; the difference is speed control.
#2, the only point when a fan install becomes unsafe would be plugging high-current server grade fans into a consumer MB header. I'm talking fans that draw > 1 amp.
#3, personally, I'd say that you should be able to plug two fans into each MB header without issue, as long as they draw 0.3A or less. May want to check with your MB manufacturer.
 
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OP
techiemon

techiemon

Member
Joined
Jan 29, 2007
This is what is listed on MB. Right now the CPU push/pull fans are on the AIO pump connector, good or bad, I don't know. And CPU-Fan.

The new Cooler Master Sickleflow Rear fan is now on the CPU-OPT connector. (By the way, this fan is nice, it provides much more CFM than the original FSP case fan, I can actually feel the difference on the outflow. But I wonder if this also has something to do with the fact that I took it off the Molex connector and put it on the MB connector... ? This fan is listed at 0.15A. But I am confused the crappy one I just pulled out is rated at 0.4A. Why so much higher? Bad quality so they don't know how to control the Amps?

1 x CPU Fan connector(s) (1 x 4-pin)
1 x CPU OPT Fan connector(s) (1 x 4-pin)
2 x Chassis Fan connector(s) (2 x 4-pin)
1 x AIO_PUMP connector

What is odd is that I just looked over the manual, there is no voltage listings for any of the fan connectors. Most of them only have 1 fan, but a couple of them have 2.


My Noctua 140mm case fan is plugged into a SATA connector, the fan is listed at 0.14A. Is this ok? I had to rig that up as it seems they only provided a 3pin on that, but provided connectors for SATA and other.

- - - Auto-Merged Double Post - - -

Edit: Any ideas why the FSP original case fan had a Molex connector instead of a 4 pin pwm connector? Were they trying to save the MB connectors for other fans?
 

JLK03F150

What have I done! Member
Joined
May 17, 2005
Location
Georgia
I used to never plug any fans into the mobo headers. It comes from old school overclocking where all the power for the mobo went to the mobo, and nothing was wasted on running a fan. Fans would be plugged into a fan controller which was directly powered by the PSU. The down side was auto control of the fans. Had to manually slow fans to make them bearable for everyday use, then max them all for benching.

I'm planning to get a sata powered tach/pwm splitter to run multiple case fans which are powered directly from the PSU, but speed controlled from a mobo header. Similar to this one.

Edit. Was that FSP fan a two wire only? No need for a mobo header connector is the mobo can only run it at 100%.
 
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OP
techiemon

techiemon

Member
Joined
Jan 29, 2007
I actually have one of these, but not sure how it would actually work, because it seems I still have to plug it into one of the MB Fan connectors to get power to it. And as I only have one case Noctua fan, I cannot make sure of the voltage limits. As I want CPU fans connected to the MB. this device is nice, but I don't want to keep messing with the speeds, opening and closing the case continually.

https://www.amazon.com/Noctua-NA-FC1-4-pin-PWM-Controller/dp/B072M2HKSN/ref=sr_1_8?dchild=1&keywords=noctua+splitter&qid=1605454004&sr=8-8

I am not sure how much MB voltage is being taken up running a fan, I don't think it should impact the MB so much, will it?
 

JLK03F150

What have I done! Member
Joined
May 17, 2005
Location
Georgia
Here's a link to the manual for the Noctua controller in you link. Look at figure 4, it is using a mobo header connector to control fan speed and a sata connection to power the fans. The output can accept 3 fans. I'm guessing you max the variable speed control on their device, and let the mobo PWM output control the fan speed.

A motherboard fan header can only handle 1.0 amps. If you connect multiple fans to one header using splitters and the fans amperage adds up to more than 1.0 amp you can damage the fan header. It's fine if you keep each header under 1.0 amp.
 
OP
techiemon

techiemon

Member
Joined
Jan 29, 2007
1. 3-pin is DC/voltage controlled and 4-pin is PWM. I have no idea what you're referencing when you say a third mode or ide (ide was an old interface for storage). Some motherboards 4-pins support both (see your manual)
2. Yes. Look at your manual to see how much each header supports power wise. If it doesn't say, assume 1A/12W.

You've been a member here for 13 years and paid someone e to build your system?!?!?!? :eek: :D

Computer fans need two wires to work, +12v & Neutral (aka ground, earth).
The third wire on a 3 wire fan is the tachometer. Plugged into a motherboard, the tach will tell the motherboard the fan's rpm and the motherboard can vary the fan's speed by lowering the +12v to the fan.
The forth wire on a 4 wire fan is the PWM signal (third wire still a tach). Simply put, a PWM fan varies it's speed by pulsing voltage instead of lowering voltage.

What you are calling an IDE connector is called a Molex connector. The molex will only have 2 wires. If the fan is a 3 or 4 wire, there will be another fan header connector for the tach and/or PWM control.

I hope that helps a little.

Here's a link to the manual for the Noctua controller in you link. Look at figure 4, it is using a mobo header connector to control fan speed and a sata connection to power the fans. The output can accept 3 fans. I'm guessing you max the variable speed control on their device, and let the mobo PWM output control the fan speed.

A motherboard fan header can only handle 1.0 amps. If you connect multiple fans to one header using splitters and the fans amperage adds up to more than 1.0 amp you can damage the fan header. It's fine if you keep each header under 1.0 amp.


Yes, I think that is right. So that wouldn't be a bad choice then to use it. But.... I only have one 140mm Noctua I would connect to it. The other fans are MSI Torex fans. They pull more juice than the Noctua I think, I need to look it up again to see if I can still plug them into that little box or not. If I can, that will relieve the board voltage of at least 2-3 fans. 1A is hard, if Torex is .4, and I am not sure it is, but I suspect, then I can only run two fans, but better than nothing.

Yes, I want the board to control the speed, because if I use AC, the CPU will be cooler, but at night I shut it off, so fan speeds need to max out at night to keep things under 80C as I crunch those work units.
 

WhitehawkEQ

Premium Member
Joined
Dec 6, 2010
Because I don't have time to build the system. I choose the components I want, through reading and asking on this board and then let someone install it all for me. They can do it a whole heck of a lot faster than I can, and I have no patience for small items and things like that, I am not 20 anymore either. haha.

Hey, I'm 63 and I do build my own systems despite having Lupus, back surgery, open heart surgery (quad bypass), and these
hands.JPG
I could build your PC in 1.5 hours. :comp:
 

Ben333

Folding for Team 32!
Joined
Feb 18, 2007
BTW, your CPU_OPT header is where you should plug in your AIO cooler pump. This is so you don't accidentally try to DC-control it to a lower power %. That header should always push 100%, there may be a setting though.

Other than that, yes as others have said, some fans come with the molex plug because you only have so many MB headers. Some fans you'll find 3pin & molex both on the same cable, and you only use one or the other. Just gives the user options. On molex you will always be @ 12V. On 4 pin you can do PWM or DC power control. On 3 pin you can do DC control.
 

EarthDog

Gulper Nozzle Co-Owner
Joined
Dec 15, 2008
Location
Buckeyes!
I don't run my pump at 100%... I get adequate flow rates around 50% (D5). Saves a bit on noise and a few W of heatdump as well.
 

Ben333

Folding for Team 32!
Joined
Feb 18, 2007
I thought OP had an AIO cooler. I think he actually has a heatsink, after re-reading. My AIO pump is near silent (quieter than my HDD) at 100%, I'm not sure if it is variable actually. You've probably got a lot more headroom with the D5.

Mainly I wanted to point out that AFIK the CPU_OPT header, at least by default, should always be running @ a steady 12v.
 

EarthDog

Gulper Nozzle Co-Owner
Joined
Dec 15, 2008
Location
Buckeyes!
I thought OP had an AIO cooler. I think he actually has a heatsink, after re-reading. My AIO pump is near silent (quieter than my HDD) at 100%, I'm not sure if it is variable actually. You've probably got a lot more headroom with the D5.

Mainly I wanted to point out that AFIK the CPU_OPT header, at least by default, should always be running @ a steady 12v.
Not sure on that last part. It's hit and miss IIRC. I know the Asus Apex has one or two like that, but I don't recall others off the top of my head. Typically users want to control the pump and any pump headers tend to have more power output. Regardless, that is good to loo out for. :)
 
OP
techiemon

techiemon

Member
Joined
Jan 29, 2007
Hey, I'm 63 and I do build my own systems despite having Lupus, back surgery, open heart surgery (quad bypass), and these
I could build your PC in 1.5 hours. :comp:

OFF TOPIC! But congratulations, I still have no time to deal with that, and frankly do not want to do it anymore.

BTW, your CPU_OPT header is where you should plug in your AIO cooler pump. This is so you don't accidentally try to DC-control it to a lower power %. That header should always push 100%, there may be a setting though.

Other than that, yes as others have said, some fans come with the molex plug because you only have so many MB headers. Some fans you'll find 3pin & molex both on the same cable, and you only use one or the other. Just gives the user options. On molex you will always be @ 12V. On 4 pin you can do PWM or DC power control. On 3 pin you can do DC control.

I do not have an AIO cooler, I have a heatsink cooler that is plugged into the AIO connector. So basically whatever I have now, will work, no worries at all, so that is good to know.


I thought OP had an AIO cooler. I think he actually has a heatsink, after re-reading. My AIO pump is near silent (quieter than my HDD) at 100%, I'm not sure if it is variable actually. You've probably got a lot more headroom with the D5.

Mainly I wanted to point out that AFIK the CPU_OPT header, at least by default, should always be running @ a steady 12v.

Again, heatsink cooler using one AIO connector.