Using PWM on a Molex-powered fan set

[misfit815]

I have a Rackable Systems 1U server (ok, actually 4 of them) that has 4 fans on the back of the unit. They're powered by a Molex connector, using only the 12V line and a ground. The do not have any built-in speed control.

The motherboard has a spare connector for PWM (it already provides this for the CPU fan).

When the fans are spun up, this thing stays amazingly cool. The problem is that 4 fans x 4 servers equals 16 jet engines that are *way* too noisy for their environment.

So, the one and only solution that I can imagine is to wire in PWM to the Molex connector. I'm going to be hitting the local Radio Shack and Frye's today with more hope than confidence.

I'm wondering if anyone here is familiar with this tactic, its success, and/or any online sites for purchasing the needed parts. So... any help?

J

 

[Sniper]

Have you looked at the BIOS for fan control options? Are the fans at full speed all the time?

 

[misfit815]

The motherboard has 3-pin connectors for 4 fans. Of those, 3 can be controlled through the BIOS. The CPU fan is one, and the others are not being used.

The 4 fans that I'm talking about aren't connected to the motherboard at all. Like I said, they're powered via the 4-pin Molex connectors straight from the power supply (using only the 12V and ground).

J

 

[Sniper]

ahh ok, I think might able to pick up some kind of adapter, I've been able to find some for regular desktops e.g. Newegg.com - APEVIA FC-01 Multi Fan Speed Controller - Case Accessories

for servers I found this Rackmount Fans: Rackmount fans, fan and filter panels from Rackmount Solutions

I think you want something like this with fan control Akasa AK-CB001 Single PSU 4-pin Molex to x4 fans (2x standard speed +12V, 2x reduced speed +5V) - Scan.co.uk or Computer hardware and software at amazing prices, available online - Scan.co.uk)