smell is AC/heating vents

One rainy day our 96 Caravan, suddenly gave off a bad smell from the front heating vents. No difference is noticed when the vent settings are changed. For a number of years, a leak occurred under the rubber insullation under the carpet at the passenger's feet. I dried it out as needed and no odour comes from there. The three drain holes, two under the wipers and one under the evaporator remain clear. Water that had settled in the blower motor cover was removed and drain holes drilled in it. Some sign of mould appears on the foam insullation of the inside/outside air vent but when I rub it with my hand, my hand does not smell. No sign of mould is on the evaporator. A small amount of wet leaves with the same odour was removed from the base of the evaporator and the area thoroughly rinsed. Two cans of AC/Vent cleaner (one from Mercedes, one from Car Quest) were used as directed. Lysol was sprayed directly on the inside/outside air vent and evaporator. The van has been stored indoors this summer for three months but a smaller noticeable amount of smell still persists. The blower motor was removed and is normal. This van is running well otherwise. I appreciate your help.

After all that how could there be a smell, but there is. You missed something. I find it is usually the evaporator and hard to get to with out removing it. If you do remove the smell one trick I have found to keep it away is to run the fan for about 10 min without the A/C on after you use the A/C. Time consuming but it works to dry out the evaporator.

Try this:

Airsept (http://www.airsept.com/index.php?loadmod=ac)

Considered your advice RickMN but didn't have nozzle needed. Took the dash and AC/heating unit out. Several areas on the 'downwind' side of the evaporator were moldy along with some wet leaves. The steorofoam around the evaporator was moldy with lots of the AC tracer so the evaporator was leaking. It took a lot of time and effort and even with the service manual I broke one or two things. The van will have to go a long way to justify the effort.

First time I've heard of someone going to that extent to fix a vent smell and from what you described it was well warranted. You didn't happen to take pictures you could post did you? Many run into this problem. Pictures of the potential culprit sure would help. Thanks for posting the fix.

Sorry RIP, I did not take pictures. I found some small pieces of leaves past both the evaporator and heater core. It took me 2 weeks. My air conditioner guy said his guys can do it in 8 hours. Replaced the evaporator at the time so the A/C should work better.