We have seen several outdoor AC condensers through the years that the coils have been damaged from dog urine. A system we installed 12 years ago was recently found empty of refrigerant. After doing some inspecting we found the coils had been broken down in 2 corners due to a dog urinating on it for a long time. It probably takes years of exposure but due to the corrosive nature of the urine the copper/aluminum coil became brittle causing it to fail and the refrigerant leak out. The customer had no choice but to replace the system.
We recommend that you watch where your pet goes and if it is on or near your a/c unit then take steps so that the dog is not peeing on the unit. Preventive maintenance is the best measure in this case so that you do not run into an expensive repair or replacement of your a/c unit.