I am assembling a computer in an ft02 case. The ft02 has 4 fans, each with 3 pins, but my motherboard has 2 fan headers I can use--2x cha_fan. It also has 2x pwr_fan, however, as I understand it, the pwr_fan cannot be used for this purpose, leaving me with 2 fans I can control.
The ft02 also has a molex to 3x 2 pin adapter, which I assume is for something fan related. I am not quite sure what to do with this. Do I plug in my fans to it and then it into the power supply? And then plug the fourth fan into the motherboard? Would that allow me to control the fans from the ft02's built in fan controller? I would like to be able to control all of the fans if at all possible.
What would the best way to go about plugging my fans in be?
I'm surprised to see your mobo has TWO ports labelled PWR_FAN. In general, such a port really has one intended purpose. It is merely an INPUT to the mobo for the speed pulse signal from the fan inside your PSU. Some PSU's actually provide a set of three wires ending in what looks like a standard 3-pin fan connector to plug into such a mobo port. IF you have that, your mobo can measure and display the PSU fan's speed, but it does not CONTROL that speed. Control of the PSU's fan speed is done within the PSU, if at all.
On many mobos the PWR_FAN port also has the Ground and +12VDC lines powered, so that, if you are NOT using it as a connection to the PSU's fan signal, it can be used as a power supply to a 3-pin fan. However, it does NOT exercise any control - the supply is always at +12 VDC, so any case fan connected here runs full speed. So you could use it that way. But I still am puzzled why the mobo has TWO such ports.
Anyway, back to your main questions. With two mobo ports for CHA_FAN, what you could do is use a fan splitter adapter or do some soldering yourself to connect together two fans in parallel, twice for the 4 fans. Most mobo CHA_FAN ports can handle the load of two fans in parallel. To do this, in each case you splice together into one connector the two Black (Ground) wires from each fan and the two Red (+VDC) wires, but keep only ONE of the yellow wires connected. (The second fan's yellow wire is just coiled and taped up, and not connected to anything.) This puts only one fan's speed pulse signal (on the yellow wire) feeding back to the mobo to be monitored, because the mobo cannot deal with two mixed signals. Then each pair will be controlled by its respective CHA_FAN port.
The alternative uses the adapter you describe. I understand it has a male Molex 4-pin connector to plug into a PSU power output, and three 2-pin outputs that probably connect to the first two (Black and Red) lines of each of 3 fans. That provides the full +12 VDC supply to all three fans. Then you depend on the fact (described in the review Scout3 linked) that the case has some switch on the top to set fan speeds to Low or High. That is not a full-range fan controller, and it certainly is not automatic, but it does give you manual control of these three. If you're doing this, I'd suggest connecting the 3 fans across the bottom of the case this way. Then, as you suggest, plug the top fan into one of the mobo's CHA_FAN ports and use it under mobo automatic control. Or, you could even have one of the bottom fans plugged into the other mobo CHA_FAN port.
There is one problem that nags me about my suggestion for splicing fans together and plugging them into the mobo ports. To do that assumes that all the fans are wired completely independently. BUT the review suggests that somehow there is a link among them such that they all are connected to the case's Low / High switch and controlled together that way. If that is the case, you may NOT be able to connect pairs of fans together and plug into separate mobo CHA_FAN ports, unless you understand and modify the fan wiring to eliminate the links among them.