Strange problem with Akasa Vipers in Push/Pull configuration

[Skittle]

I have two Akasa Viper PWM fans that I'm trying to set-up in a push/pull CPU cooler config. My motherboard is a Gigabyte GA-X58A-UD7 (Rev. 1.0). I have gotten the Akasa AK-CB002 PWM Fan Splitter Cable splitter cable and I've plugged the motherboard connector into the mobo CPU fan header. One of the Vipers is connected to the CPU Fan connector and the other is connected to one of the Case Fan connectors.

In the BIOS I have Smart Fan Control Enabled and I have set the control method to Auto & PWM and the result is the same:
The Viper connected to the CPU Fan connector runs at 100% all the time and the fan connected to the Case Fan connector shows variable speed.

I thought the whole point of buying the PWM splitter cable was to get both fans to run in sync.

Also, the CPU I have is an i7 930 OC'd to 4GHz.

Should both fans be plugged into the Case Fan connectors on the cable?

 

[Skittle]

Yep I've checked them again. There's 2 Case Fan connectors (3 wires), 1 CPU Fan connector (4 wires) and a 4 pin molex power connector.

 

[Skittle]

I've switched the fans around and the problem switched fans too so it's not the fan, it's whatever fan is plugged into the CPU Fan part of the PWM splitter cable just goes to 100% all the time.

So I've put both fans into the two Case Fan part of the splitter cable and both are running slow as expected. I've played around with Easy Tune 6 and they speed up when I adjust the fan speeds.

 

[Skittle]

Ok I seem to have fixed the problem. I plugged the fan directly into the motherboard CPU fan header and it worked fine. I then reconnected back in the splitter cable and connected the fans the way they were supposed to be connected and both fans worked as expected. I think some of the problem stemmed from the fact that I had a 3 pin fan in there before and I reseated the green RPM sensing cable in the motherboard connector as it was a bit lose.