I haven't seen one, but if it's like other RV and window units, it's sealed. And highly unlikely to leak unless damaged or very corroded. Compressors don't fail all that often in RV units, but IF it has leaks or needs a compressor, as Chris says, It's Shot.
If you want to try and troubleshoot it, I see three possibilities:
1. Compressor - Should have a label with two or three amperage numbers:
a. Running - What a normally running compressor should draw if properly charged. You can measure for that with a meter like this:
b. Locked Rotor - What a compressor will draw if it cannot start.
c. Startup - Possibly included but a common meter won't measure it unless it's featured to measure "inrush current"
See if the compressor gets started and what amps it draws. If it doesn't start and draws Locked Rotor Amps, it's either seized or bad capacitor. If it starts and draws less than Running Amps, then refrigerant has escaped, compressor valves are bad, or the motor part of compressor has separated from the pump part.
A bad Capacitor will keep Compressor (or Fan) from starting. If it draws Locked Rotor, you can try replacing Capacitor. Look to see if it appears bloated or a fluid has leaked out near the terminals. It's bad if either. Get the specs from its labeling. You can get one at an appliance parts store. I'm blessed to have a professional meter that measures capacitance, and some reasonably expensive ones do it as well.
I've heard of starting a stuck compressor by smacking it with a rubber mallet right when it's trying to start. Suggested it to somebody here and they reported it worked.
But your CC is also a heat pump, so there could be issues with the reversing valve, controls, maybe a defrost feature. Can't help much there. If a a large residential system has the valve stuck between Heat and Cool, there's a distinct rushing sound. Rapping on it while applying and removing the power might free it up. Again, it's a case where if it needs the sealed system opened up, most of us would treat it as Chris said, Shot.
