The tech used a nitrogen test to detect the leak in my system. The leak was described as "pretty significant", but in the end he could not isolate what part was leaking. I believe he did the best he could. However, I'm sure there are techs that are really proficient at finding these types of leaks by using various methods (e.g. dye) and relying on past experiences. The AC works fine when it's charged. The leak is the only issue. His recommendation was to spend nearly $4,000 (wow) to replace the inside coil and line (basically everything excluding the condenser), which is roughly the cost of a brand new cooling system. That's not what I was expecting. This company has received really good reviews and that's why I went with R&R in the first place. In the end, I paid $225 for the test/diagnosis but still don't have a working AC unit. So based on my experience I can't really recommend this company. Just want to point out that both the person I spoke with on the phone and the technician were very friendly and courteous. I was truly hoping for a better outcome. I expected to pay at least several hundred dollars to fix this issue, but not the cost of a new system. I'm sure my experience would have been much better had he been able to find the leaking component.