The clicking noise is the overload cut off or OTC. It opens the circuit to the compressor if the temperature is too hot or the compressor is pulling too many amps. This is to protect the compressor. It clicks on and off. You should hear one click and then the compressor would start running. Most people don’t notice the click when everything is fine. But when the compressor isn’t working properly you’ll hear a click every few minutes and the compressor won’t start. Reasons compressor overheats - dirty coils, condenser fan failed, Freon leak, capacitor weak, run/start relay bad, bad compressor. Most ppl don’t clean coils untill the damage is done. When the system gets hot the gas doesn’t flow properly, copper tubing stresses causing leaks and/or erosion and restrictions. Dirty coils is usually the cause sealed system/compressor issues.