I was asked about an A/C system. Since the system was drained all the Freon was taken out of the system however you still have the lubricating oil in the system. This oil which can be up to three or four ounces will find a way out if there was a leak in the system that caused it to "die". The oil is clear and very light weight, but it does leave a slight residue and is hard to clean up. Any solvent solution will clean it up. Good luck with your current problem.