If it is not hot outside, it's difficult see if AC works properly - at low tewmp. gases (freon as well) will produce lower pressure on the low pressure switch, which in turn, will cause the compressor to go on and off often. If you just got the car, and it was serviced by the dealer, I would wait untill it is hot outside, and do evacuate/recharge at any AC shop - this system takes 1.6 lb of freon. When they evacuate, they can tell you how much freon came out. I f only little amount was left in the system, there is a leak. If something like 1.2 lb come out- the system may be OK since the car is 6 y. old.
If you overcharge the system it will not work.