Hi,
Try this: Get to the underside of the auto and see if you can find where the condensate drain is located. Usually this is going to be a small hose of some sort under the dash area of the auto. Try some gentle bursts of air at maybe 20-25 lbs. of pressure at the exit point of the hose. If the condensate drain is blocked with dirt,dust, mold, etc. this may clear it enough for the drain to begin working again. The odor could be that condensate tray holding water and mold/mildew forming in large quantities. I've had this happen on a couple vehicles (usually over a winter) and in each case this method cleared the drain enough that summertime use of the A/C would then flush the lines on out.
Al

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2007 Mini Cooper 4K miles
1993 300E 2.8 120K miles
1961 Morris Minor 42K miles
1965 Morris Minor 23K miles
1997 Ford F150 235K miles
1987 Ramcharger 202K miles
1984 Chevy C-30 farm truck 88Kmiles
1968 XKE 59K miles
2001 Harley Softtail
2003 Harley Roadking