My central air unit is making aloud noise and compressor is not coming on

I need help wiring the transformer I have two black wires coming from unit and only one black from transformer I don't know which one goes where

How many watts are in a typical 3 ton central A/C unit, 5 ton unit and 10 unit? Does Anyone know? I'm trying to figure out how much of my electricity bill is due to air conditioning and heating cost.

:mad: Hello, I surely hope that someone can help me my central air unit stops working... It blows nothing but hot air... And I notice that the fan outside on the unit doesn't work. Could it be the capacitor going bad? Or is it something else? Please help Thanksss :(

Recently our central air unit stop producing cool air and noticed our fan was not turning outside, and was making a loud humming noise, can this fan be replaced without replacing the entire unit :confused: