Q: a/c refrigerant leak on 2001 Audi A4 Quattro

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A/C blowing hot; refrigerant low. Recharged and leaked again. Dye tested on 3 separate occasions at 3 different shops including Audi dealer, and leak not found. One mechanic told me the line runs under the dash at one point and he'd have to remove dash to check: $1000 labor whether fixed or not. Thoughts?
(2) Answers
Possible evaporator leak. Sometimes the dye is visible at the drain hose.
What I'd do is this:
Recharge the system. Run the A/C with the fan on low for 5-10 minutes, than turn off the engine, turn the blower on high and check for refrigerant with a "sniffer" (electronic refrigerant detector) at the vents. If it picks up freon the leak is under the dash, after disassembling the tech should be pinpoint the exact location by using a black light. This way you won't waste your $$$.

I know for a fact that when there is no dye in the exterior components then it is inside of the evaporator!! I know that is an expensive job right around 1000.00 another thing that could pin point the problem is a bad odor coming from the vents.