Weird Molex Fan Headers?

[Barnesy]

Hi there guys. I've recently built my first PC, and the case I bought for it contained 3 preinstalled rgb fans. What I found weird about the fans, was that they all had molex connecters which had been put in a chain. I was quite confused by this as all the tutorials I'd seen had 4 pin headers could be easily stuck into the case fan connecters on the motherboard. Nevertheless, I plugged it into my power supply's molex connecter and when I powered the whole thing on, they lit up and started spinning. When in my BIOS, I noticed that it registered 3 different case fans, but had no information on the speed and thus there was no way to control them. A problem I had with this was that they were resembly loud and I found that ever so slightly annoying, and I think that being able to activate smart fan on them would reduce te noise by quite a bit. Does anyone know a way to somehow connect these weird molex fan headers to the motherboard?

 

Thanks, Barnesy

 

Link for case: https://www.deepcool.com/products/Cases/fulltowercases/2021/12078.shtml

[WhitetailAni]

There is not, those just connect to 12 volts and ground. No control at all.

[Naijin]

43 minutes ago, Barnesy said:

Hi there guys. I've recently built my first PC, and the case I bought for it contained 3 preinstalled rgb fans. What I found weird about the fans, was that they all had molex connecters which had been put in a chain. I was quite confused by this as all the tutorials I'd seen had 4 pin headers could be easily stuck into the case fan connecters on the motherboard. Nevertheless, I plugged it into my power supply's molex connecter and when I powered the whole thing on, they lit up and started spinning. When in my BIOS, I noticed that it registered 3 different case fans, but had no information on the speed and thus there was no way to control them. A problem I had with this was that they were resembly loud and I found that ever so slightly annoying, and I think that being able to activate smart fan on them would reduce te noise by quite a bit. Does anyone know a way to somehow connect these weird molex fan headers to the motherboard?

 

Thanks, Barnesy

 

Link for case: https://www.deepcool.com/products/Cases/fulltowercases/2021/12078.shtml

 

 

 

Do those fans come with 2 connectors? Sometimes those stock case fans have a splitter that allows you to link them via MOLEX or use fan headers. I can't find the exact fan model but if they do, use the fan headers and disconnect the MOLEX. If you use the fan header AND MOLEX, it will just run at 12V with no control.

[mariushm]

The pinout of molex connectors is  : 5v - ground - ground - 12v  

 

As fans only use 12v, the 5v and its ground are not needed, hence the fan won't have there two pointless wires. It may look uglier, but it's better than wasting cable.

 

Because there's only power going to the fan, and you connect the fans directly to the power supply there's no way for the motherboard to control speed or measure speed. 

Those are done through the extra 2 wires in a fan header, which has the pinout  12v - ground - rpm sensor - pwm signal   (12v and ground may be the wrong way, I don't remember now, doesn't matter) 

 

The rpm sensor is on the fan, basically a pulse (a very brief on/off like the flash of a camera) is produced on this wire every half rotation of the fan, so a chip on the motherboard can count these brief pulses and determine how many rotations are done within a second. 

The pwm signal is from the motherboard to the fan, and basically tells a chip in the fan to vary the speed of the fan by changing how often it sends pulses of energy in the coil of wires that produce magnetic field in the motor of the fan. 

 

PWM doesn't change the voltage going to the fan, it's just a series of pulses that the chip in the fan can decode and from that determine the speed desired.

A motherboard may be able to control speed of a fan even if the fan has only the power wires, but the fan must have a regular fan plug, by changing the voltage sent to the fan. For example, it could vary the voltage between 6v and 12v - the lower the voltage, the lower the speed in general. 

 

The fans you have MAY have a rpm sensor built in them, and just not have that 3rd rpm sensor wire installed, because they were designed from the start to have only the molex connector.  The chip which produces the magnetic fields in the motor to make the fan spin needs this rpm signal to function properly, so in general this rpm functionality is free.  The pwm speed control however is optional, and sometimes they make the fans cheaper by a few pennies by using a chip without this functionality so it's not guaranteed those fans have it. 

Basically, if you really want to, you could try to carefully remove the label and the cover over where the wires go and see if it's possible to add more wires there.. in which case you could solder the rpm and maybe the pwm wire. 

 

[thrasher_565]

you can buy molex to 3 pin huh i cant seem to find any... well i guess buy new fans... they sapos to look like this

 

 

https://www.aliexpress.com/item/32799823817.html

Edited July 29, 2022 by thrasher_565