Only way to know is to put some A/C gauges on it, to see what kind of high and low R-134A refrigerant pressures that you have, if any. Alternatively, you could see if there is any pressure left in the system, by tapping down on one of the A/C Schrader valve service ports quickly, with the engine shut off.

No pressure=a leaking A/C system. Wear some eye protection, like goggles. Gloves would also be a good idea as well. If something blows or refrigerant hits your fingers, you need to have some protection. "Freon" of any kind will numb your digits like a super cold blast of freezing substance. If that happens you'll need to have some luke-warm water around, to alleviate the "frostbite".

 

check to see if the compressor is turning on.

the only accurate way to check the charge level is to recover it with an a/c machine. Systems can be low, be able to turn on the compressor and put out decent pressure on gauges; but not produce cold temps.

 

Not that this helps but I found it interesting,
I started hearing an odd tone coming form the speakers from time to time and could not identify the cause, it went away over the winter but come spring summer it came back, the same off and on whistle tone from the speakers.
I tried to record it but didn't have success as it primarily did it at highway speeds but was pretty consistent. In the process of trying to troubleshoot it, I tried truing various things off like the AC. Turns out when the AC was off the sound was gone...
Checked elec connections and grounds nothing found that was obvious, and AC was working fine. Fast forward a few months and we are on the road and I notice the AC getting warm and that darn tone present.
Check under the hood and find that the port for the AC is green in color, looks like its been leaking, I hit the local auto parts store and charge it up with a can as we are on the road in Louisiana and head to Houston from Arkansas. Noticed the tone stopped after the charge. Get home find the green residue on the AC low side port, I look into getting the fitting replaced ( turns out the 07's can't be replaced with out a discharging the whole system, newer system can replace the schrader valve)
I add a bit more charge using my gauges and also hit the port with some PAG oil before I put the cap on, this was months ago and so far now leak, I suspect when I checked the charge sometime year before last, the valve didn't seal well and leaked out over time.
The nut shell is that the tone I was hearing was the compressor cycling with a low charge... was this designed to do it? I don't know but it was a cool discovery...