Lower Fan Speed With Molex

[adris3ddev]

I have a few case fans that have no slots left in motherboard, so I have to use molex. However, at molex they turn full speed, which is not optimal for me (the fans are not loud, but due to my case configuration, I have more exhaust fans than intake, plus intake fans has a bit more of obstacles, so I end up with some negative pressure which is definetly not optimal). I have 2 wires coming from the fans. I somewhere read that you can move the + wire from 12v to lower voltage wires on molex to reduce speed of fan. I have nowhere found confirmation for this so I'm asking here - is it possible to rearrange my fan's molex connector to make it not turn at full speed? Or do I need some sort of fan speed controller?

 

[geofelt]

Yes, it is possible.
What you are doing is reducing the 12v to 7v or 5v to lower the speed.
You can probably buy such adapters cheaply. Noctua includes a couple with all of their products.
www.silentpcreview.com will likely have how to do it somewhere; they are into quiet computing.

Perhaps a better solution is to buy a zalman fanmate which lets you set the rpm continuously.
https://www.newegg.com/Product/Product.aspx?Item=N82E16835118217

 

[adris3ddev]

OK! Thanks for info.
What is the layout for molex's 5v, 7v, 12v and ground pins? My fan's molex plug appears to be modifiable. I can take out the metal connector from one pin and move to other. I assume I don't need an adapter in this case, right? Just move the voltage input to the right pin.

 

[geofelt]

Here is a link on how to do it.
http://www.instructables.com/id/12v-to-7v-Molex-Fan-Switch/

 

[Karadjgne]

Umm are all your existing fans already on splitters from the motherboard? Or are you running just 1 fan per header? Most ATX mobo's have at least 3 system fan headers, well capable of powering at least 6 mediocre fans, or upto 9 quality fans easily. There's very few cases capable of mounting 9 case fans.

 

[adris3ddev]

I have a microATX motherboard with just one fan header.
However, I didn't consider looking into splitters. If I can find one that I can buy right now with my nearly empty bank account, I may take that. I only need to reduce speed of exhaust fans, intake can run at full speed (since my fans are incredibly inaudible for their low price point).

 

[geofelt]

One issue with splitters is that all split fans will run at the same speed.
One of the fan sensor wires must be disabled to avoid speed sensing conflicts.

 

[Karadjgne]

Splitters only have 1 tach wire, whether 2 or 3 or 4way. Honestly, in a mid ATX /mATX case you only need 2x intakes, 2x exhausts. More than that has almost pointless returns. So if you are good with full speed intakes, use them on molex, but use a 2way splitter for 2x exhaust fans from mobo header. Or use a 4way splitter which has usb/Sata power, the header only uses the tach wire if your fans are pwm. If all your fans are analog, a cheap controller that fits in a drive bay works, some are even digital and can be automatically set for different modes. There are control options available other than LV or ULV in line adapters or re-pinning molex from 12v to 7v (most analog fans have issues with 5v)