The first rule to finding a leak in full foam is that water will show up somewhere. Go to your local nursey and get a $10 plant meter that tells you when to water your plants, or google moisture probes. It is also known as a moisture meter.
Having been a SD dealer for 16 years, we have had more than our share of leakers. After going through three of the $10 meters, we bought two $600 moisture meters with six inch probes. We got so good at it, we developed superman's xray vision and just knew what was leaking.
Some tech's use a wooden dowel but once it is wet, you can not continue to look for other leaks. Once the leak is corrected, you let it run for a couple of weeks before you return to use two chemical compounds to spray foam, the same as the manufacturers use.
We had so much experience at this, we became experts at leak repairs and were in and out in no time flat.
