In hopes/search of fixing a refrigerant leak in my AC, I want to replace the schrader cores and recharge the system but with dye so that, in case the schrader cores don't fix it, I can hope for traces of it in the system to point to a location. But in case the schrader valves do fix it, would it be bad to just keep running the refrigerant with the dye added permanently rather than recovering it and putting unadalterated?

  • Interesting. I would imagine the dye makers have not done long term testing on the dye/s, so will not say. I think it might come down to when system replacement/major repairs are expected(besides leaks). If sooner then leave it in, if plus five years, maybe not.
    – crip659
    Jun 3 at 20:55
  • If you do this, add a note somewhere obvious, and date it to show that the system was left with dye, what colour it is, and even what brand. A future service-person will thank you.
    – Criggie
    Jun 4 at 23:31

1 Answer 1


If you follow the directions on how much dye to add to your system, there's no problem with leaving the dye in there if no leaks are detected. There's nothing in the dyes that would harm the unit. If you've used dye before, make sure you clean all of it off so if there's a new leak, seeing the old dye won't give a false location.

  • 1
    What Jack said. They added a pound or so of dye to my vacation condo system about 8 weeks ago. Came back 2 weeks later after the system had been running normally on the heat mode & looked for evidence of dye leaks, but none were found. Tech said pressure was holding and just let it go with the dye in it. If it would start to lose refrigerant, the dye should show where, hopefully.
    – SteveSh
    Jun 4 at 0:03
  • 2
    Automobile AC systems commonly run with flourescent dye in the coolant.
    – Jasen
    Jun 4 at 4:09
  • One thing that bothers me here is that if the dye is non-volatile it won't show a leak in the vapour part of the circuit. Jun 4 at 8:02
  • 2
    @MarkMorganLloyd oil is not volatile either and it still circulates in the vapor part of the system. It forms something like a fog inside.
    – fraxinus
    Jun 4 at 9:16
  • @fraxinus Hmm. Atomisation through the expansion valve. Jun 4 at 10:40

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