Most people think refrigerant simply goes away, but this is not the case. In a sealed system refrigerant will not go away, instead it escapes through openings in the system like holes, cracks, or seals. Aged parts with much wear and tear and second-rate compressors built with inferior quality and substandard materials can begin to leak at the seals.
Some leaks are easily found and some much harder to find. One of the harder leaks to find is a compressor shaft seal leak. The shaft seal is located behind the clutch hub, under the dust cover in most cases. This is why it is visually hard to spot.
Have you ever heard “I can put Freon in it at the beginning of the summer, but over the winter it goes away.” Shaft seal leaks are normally slower leaks. Pulling the clutch hub will tell you what you need to know, and hopefully help you find that hard to find leak.
Here are some examples of what to look for.
Oil excreted from compressor shaft seal.
Soil buildup at compressor shaft seal leak.
Shaft seal leak detected after UV dye injection.