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Fan cable problem

M

maenos

n00b
Joined
Feb 19, 2004
Messages
31
I hope this is the right spot for this question. I've recently built an HTPC using an Asus P7H55-M Pro MB and nMediapc 1000 case. The case fans have 4-pin molex connectors, yet I want to control their speed, so I need to plug them into the MB via an adapter cable.

Here's the problem - the Asus CHA_FAN MB connector is 4-pin. I've searched and found 4-pin molex to 3-pin MB cable adapters (which looks to be the standard), yet cannot find 4-pin molex to 4-pin MB cables at all.

Do they exist?
 
If I'm understanding your question correctly - no, what you're looking for does not exist.

The 4 pin molex connector (for fan power) really only has 2 pins connected to the fan, the 12V and a ground. The fans are not smart fans in any way, provide them 12V, they use so many amps, and they're happy.

The 3 pin adapters are there to provide more wattage to a high-power fan without burning out your motherboard header (the fan speed signal wire plugs into mobo, the fan plugs in via 4 pin molex). Really only useful if you're out of motherboard headers, or on an older motherboard (Delta fans were notorious for this years ago in the Pentium II/III days, I believe modern motherboards have a fairly high wattage per header now, so you don't have to worry as much).

The 4 pin header on your motherboard provides a 12V pin, a ground, a signal line (to read how fast the fan is going), and another wire to control fan speed. The fans that work off these are pulse width modulated (pwm), basically the header tells the fan to turn off and on rapidly, effectively making the fan "see" a lower voltage. Basically, you can't adapt a normal case fan to 4 pin and have it work properly. 3 pin fans will plug into the 4 pin header without a problem (they will show speed to the machine, but not allow it to adjust speed).

If you want to control your fan speed, I'd recommend looking into some sort of fan controller.
 
Last edited:
^ Yeah you'll either need a fan controller or 4pin pwm fans.
 
Great - thanks for the help. I'll look for a 90mm pwm case fan - the one installed now runs at 100%, 100% of the time and is just too loud. Bear this in mind future nMediapc case buyers.
 
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