[folivier]

You can use the no-rinse evaporator coil cleaner in a spray can to spray and clean the compressor outer coils but need to pull the unit out to clean the inner evaporator coils. If the compressor coils look dirty and stopped up that could be your problem. In my home a/c's the compressor coils usually get pretty dirty and that's the first thing the a/c guy does is clean them. Watching the gauges the pressures usually go down to normal once the coils are cleaned.
Try cleaning the coils and see what happens.