I have a 410a leak with my Trane XL14i system. The leak has been there since the installation. Each season they need to add 410a. I have a HVAC company doing the troubleshooting for me. One of their techs told me that a Trane XL14i system shouldn't use dye to perform the troubleshooting. Unknowingly one of his techs used dye to do some troubleshooting. They haven't found the leak yet. They're planning to check the unit every month until March or April and then do a pressurized test to hopefully find the leak. They already did a pressurized test in November but the tech told me the test was not conclusive and should be done again in warmer weather.
Questions:
1. Will this dye damage the high efficiency system?
2. Does the type of dye used matter?
3. Any tips or thoughts I can pass onto the HVAC company would be appreciated.

Will this dye damage the high efficiency system?

I am not for the use of anything that is not in the unit to start with. I will say that on very difficult to find leaks dye is an alternative that is used by many companies. As far as damage to the system from using dye is concerned the manufacturer is the only one that can make that decision.

Does the type of dye used matter?
Hopefully it was designed to be used in an A/C or refrigeration equipment. If not then it could be a problem.

Any tips or thoughts I can pass onto the HVAC Company would be appreciated.

Actually the company that is working on your unit should not need any tips but if you feel they do then I suggest you look to having another company do your work since it seems you have lost faith in there decision making capability and knowledge.
But on the other hand you can tell them to have a good look at the indoor coil and any field made joints.

Dye isn't used for small leaks.

Electronic leak detectors are much more sensitive. As an example:
http://www.inficon.com/download/en/H...b%20(0407).pdf