It is plugged into my motherboard, I have a fan controller built into my case, I't doesn't have enough plugs for this next fan, can I buy a PSU cable splitter, so I can add it to the output plug that controlls the fans? They are only $2 so I think it might be worth a try, and I doubt that it could damage it, anyway if not, I have speedfan, which, I cannot get to control any fans, is this because I have many other programs doing the same thing?
Not 100% sure what you are doing, but I'll give it a shot. Splitting the output from a fan controller should be ok, but splitting the output from fan plug on the mobo is not ok. I've seen people draw too much current on the mobo fan outputs and essentially fry them (on good mobos too, ie: asus)
If was wrong in understanding, perhaps draw out how you're going to hook it up in paint (a sche-paint-matic).