Any recommendations on brand of UV dye and simple to use dye injection kit? Can dye be successfully injected with a syringe and port adapter with engine off?

 

You can add oil w dye directly to the compressor with a manifold gauge. Make sure you cycle and purge a little refrigerant through the service line first so you don't add any air into the system accidentally. They also sell oil injections that have a small amount of refrigerant, like an oz and 2 oz of oil, which is safer to use IMO since you're not putting an incompressible liquid in a running system(the oil is aerated with the oz of refrigerant). These can come with dye.

 

Thank you for the guidance! No sign of leak with detector or soapy water -- not sure if UV might catch something the other methods missed.