The weakest link in most automotive AC systems is the evaporator- the heat exchanger that cools the inside air.
It is the weak link for many reasons

1) Its a heat exchanger - lots of connections and pipe joints, thermal stresses.
2) Its crammed into a small space, near the always-hot heater core
3) if it gets dirty, it will get clogged and freeze up, the ice formation inhibits cooling and further temperature-stresses the metal
4) its in the most difficult/expensive place to find and replace =)
5) Its also in the toughest place to diagnose (in order to see dye leaking out, you have to look into the vents or the drain line....


In my limited shadtree mechanic experience, 7 times out of 10, if there is an AC leak, its from the evaporator. Inject UV dye and look down the vents (each one) around the drain line, run the system a lot to disperse the dye.

I've also seen leaks around the compressor shaft - the UV dye will show up between the A/C clutch pulley and the compressor housing.

you need to get that dye in the system if you want to know for sure

-John

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2009 Kia Sedona
2009 Honda Odyssey EX-L
12006 Jetta Pumpe Duse
(insert Mercedes here)

Husband, Father, sometimes friend =)