# controling chassis fan speed from mobo



## ptolamy (Mar 28, 2011)

Hi there,

I have a Thermaltake DH202 Case and an Asrock X58 Deluxe motherboard. The 3 chassis fans only have 4 pin molex power connectors but there are headers on the motherboard to either throttle / supply / measure the chassis fans speed.
UItimately I would like to have the fan speeds controlled by the mobo using thermal/load readings.

The 3 pin fan headers labeled CHA FAN 1, NB FAN, CHA FAN 2, PWR FAN.

Are these to...?


to power the chassis fans
just to read rpm data from the chassis fans
or both?
 
As the chassis fans only have standard 4 pin molex power connectors. Does an adaptor exist to have the speed controlled from the mobo (and bios, or internal temp)?

The bios has data spaces for rpm reports from these headers, but they are currently greyed out (as one would expect)

Do I need to get new chassis fans with an additional connector specifically for the 3 pin headers? And if I do, can these have their speeds controlled via mobo?

Cheers if anyone can help on this.


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## KD5EEJ350 (Apr 19, 2011)

CHA_FAN_1 = Chassis fan 
CHA_FAN_2 = Chassis fan 
NB_FAN = Northbridge Fan
PWR_FAN = Power Supply Fan data

PWR_FAN is only to supply a signal to the mobo from the PSU internal fan to confirm that it actually is running and monitoring.


As far as controlling fan speeds, that is a very specific motherboard feature to allow variable voltages to the pin header.

As far as 3wires, one is positive voltage, one is ground and the 3rd is for monitoring.


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## ptolamy (Mar 28, 2011)

I now understand the function of the specific colour cables, and of the PWR_FAN header. But can my mobo power the fans from the CHA_FAN headers? If so do adapters exist 3pin > molex?

many thanks


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## KD5EEJ350 (Apr 19, 2011)

ptolamy said:


> I now understand the function of the specific colour cables, and of the PWR_FAN header. But can my mobo power the fans from the CHA_FAN headers? If so do adapters exist 3pin > molex?
> 
> many thanks


There is no point in making a molex to 3pin since molex doesn't have the data cable and all power originates from the powersupply anyway, why tap the motherboard rails for no reason?

There IS a TX3 to molex to use 3 pin fans on the molex.

But the only reason to plug a fan to the motherboard is to monitor the fan speed, so if you want to monitor the chassis fans you need to get 3wire case fans, newegg.com has a huge selection of sizes, speeds, visuals and sound volume.


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