Thanks a lot guys for the responses. A couple more questions then:
1. Does the A6 allow for fans to have power supplemented to them rather than supplying power itself? Ie can it only supply a speed signal? The other reason I'm using the 5-way splitter was that it allowed a neater cable run and I didn't want to have to use lots of extenders and y-splitters to reach from fans to a6
2. I tried unplugging the 5-way molex connection, and powered on system, but the other fans still did not rotate at all.
3. Erik I tried your suggestions again but still I can't get channels 2-4 to rotate, and therefore cannot programme rpm.
4. Jasonmorris, can you explain what you mean by jumping around? As far as I'm aware the 5 fans on the Akasa 5-way are all receiving / outputting only one signal.
On the Akasa I bought a while ago they all supplied an RPM signal so it jumps about in the software. I use modmytoys 4,6 and 8 way fan splitters. Normal fan cables go into PWM splitter, which is easy to hide, and then just one normal size cable to the Aquaero - no massive bundle of cables like the Akasa. Also, no need for a molex as they Aquaero supplies all the power.
Am a bit stuck for ideas. Even when ruling out the 5-way splitter and it's own molex power supply, the other fans should work as far as I can tell.
Is there anything about y-splitters that A6 doesn't like, any compatibility issues?
Thanks guys