I am in the process of helping to write up a policy paper on the use of dye for techs and I am really conflicted. Is it not illegal to knowingly let refrigerant leak out of a unit? When using dye (I have ) are you not hoping that the unit will leak to locate it? Bottom line is dye is illegal for the purpose of locating leaks. Now in saying this I do use it as a last resort and my techs use it as a last resort afer trying the conventional methods. I also believe every job is different and common sense has a big part to play in the determination to add dye. If the unit is empty then yes the leak should be located with detectors and soap but if down slightly over the course of a season then dye might be the answer. Money is also a concern, locating a leak may cost more than the value of the system. I have found many coils are starting to leak and in some cases dye has been the only way to find the tiny pinholes located in the tubes. Please keep this discussion going lol I need ideals and thoughts for this thing.