The other systems are the high pressure side, compressor, dryer, evaporator, expansion valve and condenser. We talked about leaks last time. Leaks are mostly from sealing areas and failed parts.
The high side of the system has 200 lbs. to 300 lbs. of pressure, so it is the most likely side to leak. Condensers can also leak, which is caused by something hitting it. Leaky evaporators can be caused by temperature changes; it gets cold then warms up when A/C is turned off.
The expansion valve is what controls the pressure from the high side to low side and also is what causes the evaporator to get cold. The drop in pressure causes cold air.
The compressor is the hardest worker of the system. It has bearings and a lot of moving parts. When the compressor fails, it causes a lot of foreign material to get into the system and then a lot of parts need to be replaced. The filter dryer will filter a lot of this stuff out of the system, but all systems will need to be flushed out. The compressor, dryer and expansion valve will need to be replaced. If the condenser is full of this stuff, it will also need to be replaced. You need to replace all of this to have any warranty on the parts replaced. Do it right the first time.