2000 Grand Caravan A/C Evaporator

Had the van checked today by an a/c shop that is very reputable and a very long time family operation in the area. Still no dye showing anywhere. Pressure tested good with no loss. Was down 2 lbs. Of refrigerant (1lb left) during a 6 week period. Recharched and works ok for now. But I know it wil leak out again. Found out their is only one system on this van, no rear unit. Still leaning toward the possibility of a bad evaporator, unless anyone has an idea of where else it could leak without leaving a trail of dye. Also, why would the system hold fine during the pressure test.

You are refering to the vacum test that is done before the system is charged right? If you are the system is in a vacum state for this test and the leak has to be pretty big for the leak to show up plus sometimes the vacum sucks the hole shut. If you suspect the evaporator find someone with a leak detecter and have them stick it down by the drainhole where the water drips out from the evaporator. Or tern the key on but don't start and set the controls for max a/c and tern the fan speed on low and stick the leak detector in the vent. You don't want the vehicle running for nether of these tests.

Yes, vaccuum test. Thanks for the helpfull info. I'm going to have someone else check it tomorrow and will pass on your suggestions. I'll keep the board posted as to what we find.

Had another shop check it out today and they told me I the schrader valve is bad and needs to be replaced. They said the vaccuum test looks good and are 90% sure it's not the evaporator. Told me that the valve has to be disconnected when doing the vaccuum test so I'm wondering how they know the refrigerant is leaking here. Anyway, they said the job would cost 261.35 plus the cost of any refrigerant that may need to be added when the job is done. I checked with Advance Auto Parts and their "Factory Air Seal Kit" (a/c caps/valve core kit) costs $15.48. So the repair shop apparently wants to charge me a minimum of $245.87 in labor. Sounds like way too much to me! Any thoughts out there on this schrader valve fix and how much this should approximately cost?