Air Conditioning - Compressor Fan capacitor help needed

My compressor fan starts intermittently. Sometimes it starts normally, sometimes it starts but is slow to spin up. Sometimes it doesn't start at all, but I can spin it by hand and make it go. I figured it was probably a capacitor, but when I pulled the cover off there are 3 caps. They are all wired together so I wasn't sure which one might need replacing. The fan motor is connected directly to the little can, but then feeds to the big can which is tied to the black one.
ac inside view (http://home.cfl.rr.com/dreamin/images/ac_caps.jpg)
brown wire on fan goes direct to the little one, the other side of that cap goes to the big can, which taps go to the black one. the heavy blue wire on the big can goes direct to the compressor itself.

which one should I replace? or all? thanks.

well if you can check to see witch one is not getting power id say thats the bad one but if you have no way to check power id change them all or call a tech

they all get power, or it wouldn't start at all. I know there's a start capacitor and a run capacitor, I don't know what the 3rd one is for. I think the big black one is the start cap. I don't know if one of the other two might be draning the start cap enough to keep it from starting the motor sometimes.

The smallest is the fan capacitor. The larger metal one is the compressor capacitor and the big black one is a start assist for the compressor.

ok thanks,