Originally Posted by
Old Farang
Its a fluorescent dye that shows up under UV light. Like this:
https://www.ebay.com/itm/Errecom-AC-Systems-UV-Leak-Detector-Dye-R1234yf-Blue-Brilliant-Hybrid-Electric-/392326524416?ef_id=Cj0KCQjwn7j2BRDrARIsAHJkxmxJn1z D-E24FWHwdjJPaT6dUAB-V_N6YDLncS3z3sU-0Zv3eHnih6kaAotXEALw_wcB:G:s
Several yeas ago the air con in my Land Rover was not putting out as it should. The car was in at the then dealers and I asked Einstein to check it while I was there. He started waving a UV lamp around, so I asked him: "when did you put the tracing dye in?" He responded with a blank look, had no idea what I was talking about. At that time I was not long into retirement and still current of what was what. I know for a fact there was no dye in the system.
Just happened to mention it recently to the English tech at the now dealer, and he claimed that it is now included at the factory.