This is the biggest headache that everyone faces, practically it is too costly to even fixed it.

• Troubleshooting by holding 24-48 hours pressure to see where the leak is (Cost factor $500-$800 for 3-4 days job)
  • If there is a leak in the condenser unit,
    1. There is possibility that you may change the condensing unit if still available ($1500-$2200 to replace outdoor unit)
    2. There is possibility that you may repair the leak ($200-$300)
  • If there is a leak in the piping, it might seems not economical as you would need to dismantle the trunking covers to check where exactly the leak is. Not forgetting if you have false ceiling, you might need to hack it to check it. No contractors will go down this road.

There isn’t much you can do if your piping are concealed, at this point of time, is only to replace the whole system which has much more economical sense. So always go for experience contractors who has a lower chance of making such mistake.