most of the time what i do is get the vehicle up to normal operating temp and use a laser thermometer. measure the inlet temp and the outlet temp. if theyre close to the same then your radiator isnt doing what its supposed to do.
I was told it was cracked at the top. AC that usually cools is not cooling unless the car is moving. They showed me the top where it s beginning to crack (they said) I think it is original to the car. Not overheating yet.
If the tank is cracked you will probably need a new radiator. As stated before; is it leaking? Probably not the cause of your A/C not working though. That sounds more like an airflow issue. Maybe your fan isn't kicking on when you turn your A/C on, or your regular fan clutch is going out. Cheers.