My air condition unit was on and it started making a loud sound so I turned it off. I just turned it back on and all it will do is make a huming sound and it want come on. Please can anyone tell me what it could be.

Hello camper girl

The sound made and the humming now indicates that the problem is with the compressor.
Do not continue to try getting it running, or it will burn out the compressor.
Let a professional repairman have a look at it. You require special tools and other "goodies".
I fear that it's 90% sure that you require a new compressor.

:>)

If your hearing a loud hum from the compressor inside the A/C unit and the fan is not running(a lot of heat will becoming from the top of the unit). You have a bad condenser fan motor or a bad run capacitor. If its just a low slight and quite hum you may have lost power going to the out side system and your hearing the coil on the contactor. Turn the breaker going to the A/C off and then back on. (Not the breaker going to heat or furnace) See what happens.