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stinky AC/ventilation

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title says it all ;)

anyone have any tips on cleaning out the ventilation ducts? i guess that bacteria is growing after the AC has been on and condensation accumulates but where is it accumulating? are there drain holes that need to be unplugged? lysol in the ducts?

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It definitely helps to spray Lysol into the A/C system.... Turn on the A/C full blast, put it on outside air, and spray into the area at the base of the windshield where it sucks in the outside air (at least there is where it is on 99% of cars, but I'm new to Porsche)....

It's bad enough on some cars that this procedure is part of their TSBs for stinky A/C's...

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This post, and the two following, were copied from another forum.

Read the material at:


and/or search google for "defog" and "demist" and "denso".

In the meantime if you park the car in a garage at night it will help tremendously if you religiously lower the windows slightly or open the sunroof each and every night.

Edited by wwest
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As was said previously modern day A/C evaporators are highly dense, 10,000 square inches of cooling vane surface area in a fairly small compact size.


When you shut down the car and having used the A/C there will ALWAYS be a thin film of condensate left on those cooling vanes, possibly as much as a pint to a quart of water.

Since the operational temperature of those vanes is in the range of 33 to 35F it might take hours for the plenum temperature to rise enough for that mositure to evaporate. And now that it is evaporating where is it to go?

Absent any forced or convection airlfow it will, of course, remain within the evaporator plenum area. Providing an excellent breeding ground for the little tiny microbes that provide the "leavings" you think of as mould and mildew odors.

One night alone will not do the job, but if you leave the car open each and every night I can assure you that it will alleviate your odors forever.

Well, at least it did for my 92 LS400.

But you could always have someone install the EED, Electronic Evaporator Dryer, I referred to.

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Some manufacturers, Lexus, Toyota and mazda for sure, are adding a porus nylon coating to the vane surfaces into which is embedded a chemical fungicide. Lexus started doing this back in 92 but then apparently had to stop for a few years due to not having filed a MSDS document with the US defining the safe use of the chemical.

The pollen filter was added to help matters in this regard, no food (airborne debris) for these microbes, and now I see the LS430 is equipped with a UV light source within the A/C plenum to surppress the microbe growth.

The other problem that occurrs with the porus nylon was that once the chemical was leached out due to continuous daily condensate "washings" the evaporator vanes surfaces really did become a GIANT sponge.

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so here's the evaporator assembly but where is it located? if i can spray some disinfectant into the inlet while it's blowing then that may do the trick. i guess it's downstream from the pollen filter.


Edited by karlooz
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  • 7 months later...

How would you describe the smell?

Mine is sort of smokey, like a very cheap cigar (but never any smoking in my car)

it started suddenly on a hot day and was made worse with Ozium, which I regrettably sprayed into the intake vent,

Does anybody know how to get to the evaporator on a 1999 996 coupe?

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When I complained about that smell the dealer used a product called

FrigiFresh (not 100% certain of that spelling) made by BG.

It helped a lot, but I don't think the one application is 100%.

I used Google and found a place selling it. They aren't giving

the stuff away. And when it arrived I was shocked by the small

size of the aerosol can.

I've also been leaving the windows open a bit.


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  • Admin

I've done this several times on my wife's Jeep. Unfortunately the design on the Jeep allows leaves and other crud to fall inside the fresh air intake. Porsches are much better with the pollen filter stopping most of it. I use Lysol and turn the heat up as far as it will go (with the windows down). That way you cook and kill all the stuff that is growing in there.

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  • 4 weeks later...

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