There are a few noninvasive tests you can do to figure ot what is happening with the unit. Plug the thing into a power meter like a kill-a-watt or use an ammeter to determine how happy the compressor is. With smaller units, the power draw doesn't swing as much with compression ratio as much as larger compressors, but it still swings. When operation initiates, you will get a jolt from the starting circuit, then power draw should drop to below normal running amps. As system pressure builds, the power draw will slowly ramp up to running amps. This value should be on the compressor nametag.
A lot can be found from the temperature of the refrigerant piping at various points in the circuit. The 3 main places to look are at the compressor outlet, the inlet to the capillary tube, and the outlet of the capillary tube. The outlet of the compressor should start out at ambient and climb to somewhere above water temperature. The inlet to the cap tube will usually be a little above water temp, and the outlet should be cold. If these 3 temps are normal, the system is probably ok. If not, what temperature they are vs what is normal can give you an idea what is going wrong inside the refrigerant loop.
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