Why cant fan speeds be controlled once you use the 3-pin to molex adapter?

[Oobie-]

Hey guys,

One of these is needed to extend the fan's wire to reach the chassis fan pin header:



The thing is, once you've done this, it spins its fastest RPM. Its still got all its 3 pins in the "Fan" connector, so I don't see why it cant recognise speeds.

If you don't plug in the molex, it doesn't even power the fan.

Can anyone shed some light on this for me please?

Thanks

[Koolpc]

Faulty?

[switchmode]

What fan ? What header?

[matty-hodgson]

it probably just gets powered and controlled from the PSU totally.. so it's just powering it at full whack

edit: have you tried only connecting it to the molex?
does it do the same thing?

[Webby]

If its not powering unless you plug in the Molex then I would say that its most likely that the is a bad connection somewhere.

If you power via the molex then the fan will be powered at 12v and the will be no fan speed control.

[dave87]

The Molex is providing a constant 12v feed, so when the Bios tries to reduce the voltage to the fan, it has no effect. Thats why you can see the speeds of the fans in the BIOS, but not be able to have them throttle themselves.

[Oobie-]

Xigamatech - plugging into chassis_fan1 header on the mobo.



For removing ambiguity.
If I plug in the fan directly into the mobo fan header, it powers down to a quieter 900rpm (Chassis Q fan control on silent). So the fan works.

So the problem is cause its connected via molex dave87?
But if I don't connect it to the molex, and just go straight into the connector marked fan on the above picture, and then into the mobo, it doesn't seem to power it. Its just a friggin extender cable, no?

[dave87]

That basically means the molex is providing the power, and the one to the Mobo is simple a signal wire.

Easiest way to control the fan is to get a separate fan controller.

[s3ds]

Faulty?

Agreed most likley the connection between the wires from the mulex to female fan connector


could use one of these


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