My A/C keeps leaking out. I have a 1997 960 with 175k miles.2 summers ago the A/C needed recharging and this charge lasted for the summer. Last summer, the A/C needed to be charged twice and each time it lasted for a shorter time, the last being a week or so. It did seem to "sputter" as it did kick on once or twice for a short time, shortly before it stopped cooling completely. A dye test was done twice as well as visual inspection and possibly one other test though no leak was identified. A a/c system sealent was put in prior to the last charge which did not seem to help at all. I have noted this past year, I do get more external exhaust fume smell into the passenger area, even with the vents closed. Is there an area where the system may be leaking even if the dye test was negative and sealant didnt close it? Any way to localize this leak more easily? Any input would be helpful.