A/C Not Functioning

[TheBestCow]

On my way back to school from spring break, I thought it would be nice to cool down with a little A/C. I don't use it that often, but it has always functioned when I use it.

I hit the button. The A/C light on the button comes on. I hear the compressor click on under the hood.

... no cold air. The air is the same temperature as it is with the A/C off. As you can imagine this was a major bummer as it was a bit warm (70s, quite nice) driving into northwest Georgia.

I know the compressor is being turned on, as I can hear it engage. Just no cold air. I've been told to look at the compressor to see if it is turning - and it is. Also, whenever the A/C is engaged (as in, the light on the button is on), there is a slight hissing noise from the main vent.

Am I low on refrigerant? Do I need to check for leaks?

I'm just trying to sort this out before I take it to a shop for a diagnosis fee.

Thanks!