A/C leak in my car

[engineer_dude]

OK, so about 4 months ago, I had my A/C system recharged. I knew there was a leak somewhere. The mechanic said they looked for a leak and couldnt find one. He said it might be a really small one thats almost invisible to the naked eye. So he injected some of that fluorescent dye into the system and recharged the A/C with coolant.

OK, well 4 months later the A/C is no longer cold, so I assume all the coolant has leaked out.

My question is, since he put that fluro dye into the car, can they now see where it leaked out at? Or does the dye degrade and 4 months is too long to see it anymore? Would he have to do the dye test again or what?

 

[BigWill]

a blacklight should be able to find the residue from the leak.

 

[accuratehorn]

No, the dye stays in the system and should show up where there is a leak, even years later.
If the leak is anywhere under the hood, a shop with a black light leak detector should be able to find it. If the leak is under the dash in the evaporator core, the shop may not be able to see it unless they take that part of the system apart, because it is enclosed in a plastic housing behind the glove box. Sometimes you can see the dye at the bottom of the water drain hose that comes out of the evaporator housing if the leak is in there, but sometimes the leak is too slow.
So if they check under the hood thoroughly, and find nothing, the leak should be in the evaporator core.
Also, the schraeder valves should be routinely replaced when recharging the system, because they frequently leak after a few years.

 

[horn4life]

What accurate horn said. Sucks though....