[infinitesymphony]

A fan-related question...

The stock 380-watt Antec power supply in my parents' Antec Sonata case died, so I replaced it with a Corsair CMPSU-400CX. It works well, but the rear case fan is now spinning at 100% and cannot be controlled with applications like SpeedFan.

The Antec PSU had a 3-pin, two-wire cable that connected to the PWR_FAN header on the motherboard; this new power supply does not have any 3-pin connectors. I'm assuming the old PSU was communicating the case fan speed to the motherboard. If I use a 4-pin to 3-pin adapter to connect the case fan directly to the PWR_FAN header on the motherboard, will that give me the same amount of control as before?

An example of a 4-pin to 3-pin adapter (4-pin side on the right):

My case has turned from near-silence into a white noise machine. Any help would be appreciated.

 

[joe_cool]

PWR_FAN header is used to monitor the power supply fan speed.

 

[dBs]

The yellow wire monitors the fan speed on the 3 prong connector. The red and black are the +5V and ground respectively.

If your PSU has fan specific molex connectors than it is possible that the fan controller in the PSU is bad. I had this happen to mine after I had had it a while, except all my fans died. I had to open the PSU and hardwire them directly to the rails and now my fans are at all time 100% (which is fine by me).

If your mother board is good enough you can have the fans controlled by the motherboard via those 3 pin connectors that you show above. If the mother board isnt that sophisticated you may still be able to use the free Speedfan program to manually control the fans through the motherboard (as well as monitor just about everything in your computer).

 

[MCC]

You could try undervolting the fans. To run them on 5 volts, move the red wire in the molex connector on the fan so it connects to the red from the power supply instead of the yellow wire. There's also a way to wire for 7v, but it's best to read the cautions at the link I've provided first.

 

[infinitesymphony]

Thanks guys, all good advice. As dBs suggested, the old PSU did have fan-specific connectors, so it was controlling the fan speed before it died. If the 4-pin to 3-pin adapter doesn't work, I may simply go for an Antec TriCool fan set to low and avoid using fan controllers. Undervolting sounds interesting, but I want to avoid any potential damage to the PSU.