I had the same issue flashing. The key is the jumper but I'm not sure why since my unit is brand new. I was about to throw my XT in the garbage until I stumbled on that piece of information. ;)
Sorry, what do you mean "you may need both RPM and ground wires?" The 450S has a 2-pin molex (yellow & black) for power and a 1-pin molex (blue) for RPM (
http://www.koolance.com/water-coolin...mp-450s_p0.jpg). The 2-pin molex will be going to another device to power the pump. Can the 1-pin blue wire simply be attached to a XT fan header?
So there is no way for the XT to understasnd multiple RPM wires coming from different fans when connected to a single XT fan header via a Y-splitter correct?
Thanks.