So why did my 2004 G35 have the exact same problem? Hmmmm...

 

It seems like this is a touchy topic. My GS is having problems with mildew, but it did sit on the dealer's lot for a year.

I've had three other Lexus's and NONE had a problem with mildew smells, neither did my older Camry, or my Accord. Taking this out to my immediate family, we are looking at roughly 18 cars in the last 20 years and this is the first that has a problem. So it's not as common as many of you like to claim.

Now it's obviously occurred with many of you before your GS, but you're in the very small minority. Obviously something is different with the 4th gen GS that causes it to have the mildew problems much more frequently than other cars. Finally just to drive home this point, my Lexus dealer told me tonight that there are only a couple of models that have ever had mildew smells, but she couldn't remember which others.

 

I wouldn't call it a touchy or spotty subject. I think alot of it has to do with climate. If you're up north you may never get the car hot enough to grow mildew and may not run the AC much. Here in the south it's much more prevalent for a lot of vehicles. I could post a 20 page thread from the Infiniti forums showing that it was common for those cars as well. The CT loaner I drove had it, and my GS is starting to do it now that it's a year old, but not enough where I'm taking it to the dealer (yet).

I think it's just a design flaw, on all these different cars, with the AC design. Somewhere, water is puddling and not evaporating. Infiniti used to advise people to run fresh air instead of recycled air for the last 5 minutes before parking it (in an effort to dry out condensation I believe) but that only works if the outside air isn't swampy. Here in north Texas, it's swampy frequently thanks to southerly winds from the Gulf. So that option doesn't work for us.

Whatever the case may be, I know for a fact that alot of cars don't do this, and 80's and 90's cars didn't have this problem either. At some point a fundamental engineering change was made that caused this to happen. I'd love to know what it was, why it continues, and why it's not the focus of a major redesign. Google is full of results for this, and KBB even has an article on it at http://www.kbb.com/car-advice/articl...ide-car-vents/.

 

Sorry, but I'm not understanding how this helps Lexus with CAFE standards. An air conditioning system that is always on Recirculate uses the evaporator more often, which takes more gas. Allowing fresh air in uses the evaporator less, which takes less gas.

Just for the record, I've read this whole thread and my beef with my GS after almost 3 years is that when in Auto mode it NEVER moves from Recirc to Fresh. I have just gotten used to doing it manually after I've driven for a few minutes. (And I've done the smog adjustments mentioned in the earlier post.) I think I read somewhere in this forum that it will not move out of Recirc mode until the outside temp is 75. When the temp gets that low I just turn the AC off and use fresh air.

Mine has no moldy smell, so perhaps there really is something to be said for driving with the AC in a mix of fresh and recirculated air. I did have an Infiniti M35 that had horrible smells coming from the vents when the air was first turned on, so this is not isolated to Lexus. Also, at home when I turn my AC on for the first time after having the heat running it smells.

 

I'll look up the documents for you and post back.

I think the logic is that with outside air at, say, 88F and cabin temp initially at, say, 110F, recirc will set up a (psuedo-)positive feedback loop where the intake air is continually cooler. Once the cabin temp cools to 88F, recirc becomes much more efficient at keeping the setpoint of, say, 72F. This is because fresh air intake would require continuous cooling from 88F to 72F whereas recirc would only require cooling from the cabin actual temp to the setpoint. Surely you see that the initial SHORT-TERM inefficiency of recirc (high cabin to setpoint) is more than offset by the LONG-TERM efficiency of recirc (near-setpoint cabin to setpoint) compared to the initial benefit of fresh (ambient to setpoint) versus its long-term inefficiency (same ambient to setpoint). Consider the amount of time the car typically operates in each mode. THAT should give you the sense of why recirc is favored over fresh air intake for increased fuel efficiency and reduced emissions.

 

See "Air Conditioning Improvement Credits" on Page 7 in this document:

http://www.epa.gov/otaq/climate/documents/420f12051.pdf


and same heading on Page 62628 (yes, page 62,628!) in Federal Register:

http://www.nhtsa.gov/staticfiles/rul...Final_Rule.pdf


and under "Air Conditioning Improvements" at bottom of document:

http://www.c2es.org/federal/executive/vehicle-standards

 

They sure did a good job. I usually don't turn on my AC but now I keep it on to get rid of the smell...good job!

 

Bottom line is...this is something that happens to all cars given the right circumstances. If it didn't...they wouldn't sell products to specifically address this issue...which they have for years.

Does the Lexus defaulting to recirculate above 75 degrees make it more likely than running fresh air all the time? Probably. But, thats not a "feature" unique to Lexus...its something all carmakers are going to...our 2014 Jeep does the same thing. You have control...just select fresh air. Its annoying to do it every time, sure. But...blame congress not carmakers.

Like I said, my GS had this moldy smell when new. They cleaned the HVAC system under warranty...it was gone for about 25,000 miles. This summer it came back. I bought a $7 can of cleaner at PepBoys and emptied it into the vents...its just as gone as after the dealer's HVAC cleaning. Our new Jeep developed the same smell this summer...emptied another $7 can into it...it smells great.

So...if a $7 can of cleaner and 5 minutes of time when washing the car to empty a can into the system and let it run for 10 minutes while you dry it off is them "giving it to Lexus owners in their wallets"...I think we all need a little perspective.

To me it is a non-issue. Honestly...the can worked so well it wasn't worth the energy to even tell the guy at the dealer when it was in for its next service even if they would have done it again for free.

 

for me, the smell did not come back for a long while. the trick is that you need to off the AC and hold on for 5-10 secs before turning off the engine. I figure that you need to let the ac fan come to a complete stop before turn off the engine. i have been doing that for the past 6-7 months and that awful smell did not come back since. give it a try and see if that works for you but before that you may need to use spary some lysol, turn up the ac temp and let it circulate to get rid of the smell.