Originally Posted by jvjessen
If you have access to a multimeter, you can try measure the voltage between pin 1 and pin 2 on one of the fan outputs, it should be close to 12V when fans are set to full speed.
Another thing to consider is the cable gauge, thin and long cables do create a voltage drop, so it could be something like the PSU outputs 12V, but by the time it gets to the fan controller it's dropped to 11.5V and then there is additional internal resistance (or perhaps it's not capable of outputting the full voltage) in the fan controller loosing another 0.5V and then finally you have the cables going to the fans with additional drop. So when added up the fans only see 10-10.5V instead of 12V.
It sounds like you run the fan controller on a separate PSU? If that is the case, then keep in mind that some older/cheaper PSUs need load on both 5V and 12V for proper regulation.
Turning all 4 channels to max, I'm measuring 10.5V. When I drop down 3 of the 4 channels, the voltage increases to about 10.8V.
When I tried running a set of 3 fans on my motherboard I got close to 1600 rpm, so I think the problem does not lie in the 3->1 Y extension cables. I am running this right now on my normal PSU, and the fan speeds are a little higher than on my $10 PSU, but still not what they should be...
When I plug in just one fan into the controller I get 1560-1590 rpm and an output of 11.2V (with a 3->1 Y cable and two of the three disconnected).
Just a fan directly onto the controller I get 1590-1620 rpm and still a reading of 11.2V.
So, while there probably is some resistance in the wires, it still seems to me the problem is either PSU or fan controller related? I have tried two different PSU's now, a good one and a ****ty one, and both are not giving me the results I want, albeit the good one gives me better results, with all fans maxed I'm still running them 15-20% less of their rated specification (1600 rpm). So I'm guessing it must be the fan controller?
Is this a fair assessment?Edited by Captivate - 11/2/13 at 11:31am