Mildew smell from AC
 

I just wanted to see if anyone else has experienced this problem.

In general, the ventilation system is odorless until the AC is engaged (either with the AC button or switching to defrost). Once engaged I get a horrible mildew smell from the system. I assume the smell is activated by the condensation from the AC heat-exchange coil. Eventually the smell dies down as air flow through the system. I have had the dealer use their disinfecting spray once and it fixed it for a day or two.

I also believe the AC condensation drain is working properly and I am not getting water buildup in the system. I can see the water dripping under the car after using the AC.

Anyone else have this problem or am I just lucky? Any suggestions on how to fix this?

Don't run the A/C in Recirculate all the time, use it only to cool down, then use fresh air.

If you have have mildew in the system, perhaps putting the heat on full might 'cook' it

Agreed. I try not to. Unfortunately the upgraded AC Amplifier forces the system to RECIRC every time you turn the AC (after starting the car) on so I have Mazda engineering working against me.

At this point the smell is definitely less with RECIRC off but it's still there.

Could be time to replace the cabin air filter?

Little tip I tried just as an air freshener, was to remove the cabin airfilter and give a little spray of whatever you want your car to smell like, and when the air flows through it, it freshens the car with that smell.

By the way, you can always turn the recirculate button to fresh air once you are cool enough, even though the new amp made it start in recirculate.

It's almost a given that there is water pooling somewhere, allowing the mold to grow. So, check out the drain path carefully and then spray the drain area and drain pipe with something like Lysol spray.

change out the cabin filter, then run the heater on full for a good while. that should kill any mildew that has built up in your ventilation system.

to prevent this from happening again, after running the AC for an extened amount of time, before shutting off your car run the heater for a couple minutes just to evaporate any condensation buildup in your car's ventilation system.

just my $0.02

i think i have the same smell, except mine always reminds me of a barn because it smells like hay.

There are sprays made specifically to clear up mildew inside car AC units. I've had good luck in the past with just using Lysol spray. open the car up, turn on the AC, NON-RECIRCULATE, and spray the whole can into the intake vents, then shut down and let it sit overnight. Yeah, there's gonna be a lot of lysol smell for a little while but it will dissipate. The mildew will eventually return if the system is allowed to sit wet for any long period of time, because the "food" - a.k.a. dust, is still in there. Just add water :)

Edit: here's a link to "Frigi Fresh". Might smell nicer, but Lysol is cheaper :)

http://shop.store.yahoo.com/tri-maxx...ridsysdis.html

When the AC is running, the coils have water condensing on them. It eventually drips off and exits through the drain. But, the coils remain wet nevertheless. Add some dust and you've got a nice environment for mold when you shut the car down. One thing that can help is to remember to turn off the AC a few minutes before you get to your destination, but leave the fan on, even turn it up. This will dry up the coils before you shut down. On the RX-8, the only setting that doesn't invoke the AC is the face-only.

Mold needs moisture and a medium to grow in. Just take one of the two away, and your problem is solved. A long, dry winter often kills off the mold, provided you drive around in the long, dry winter in the RX-8.

Just an update.

Despite long periods of moderate weather (no AC) the ventilation system remains fresh until the AC is turned on. Once moisture condenses on the evaporator it still produces a bad smell. If I had a standing water problem it would be there whether the AC was on or not so I am assuming this is an issue specific to the AC evaporator coil.

I removed the glove box and pulled the filters (which had no smell). The design of the A/C system makes it impossible to actually get to the evaporator without removing the blower assembly (the heater core blocks it from below) so, not being up for that much automotive surgery, I could not actually examine the condition of the evaporator. On to plan 2.

I had obtained a can of Frigi-Fresh from the local NAPA parts store, so I turned the blower on high, and sprayed the Frigi-Fresh into the filter slot which is just above the blower intake. This forced the stuff all through the lower system. Since I don't have a ductwork smell issue I didn't bother spraying it in the various vents in the dash. Then, per the Frigi-Fresh instructions, I left the blower running for another 5-10 minutes. FYI, if you do this, put a drop cloth below the blower to catch the Frigi-Fresh that drips through.

Well the mildew smell appears to be gone. The system now smells like Frigi-Fresh for the first few minutes of operation. I am assuming (hoping) that the Frigi-Fresh smell will slowly fade leaving me with a neutral smelling system in a week or so. I am also hoping I will not develop cancer from breathing so many Frigi-Fresh fumes.

Check out this TSB courtesy of Rosenthal Mazda. This problem is not related to just Mazdas

http://www.finishlineperformance.com.../pdf/1053c.pdf

Thanks for the link. That is exactly my problem.

Unfortunately it doesn't seem to be an issue for most RX-8s. My car appears to be one of the exceptions. Lucky me!

wow, one of the few things my 8 does not suffer from ... hope that works for ya, there's nothing worse than that mildewy smell!

The Frigi-Fresh seems to have done the trick for now. Yes, it was so bad that my 8 year old didn't want to ride in the car when I had the AC on.

no heres what u do if ur cars smellin of mildew, im goin to school to be a technician, what u do is get urself some spray disinfectant.....that kills mildew, n all that stuff, preferably a smell u like, n with the car running but the air not on spray some disinfectant, into each of the vents on the dash board for like a couple seconds each, then turn on the A/C n then the problem should be solved.

Based on my experience, it is a recurring problem in the high humidity areas of the country. I lived in South Carolina for 11 years and every one of my cars had this problem. The high heat and humidity of the summers there make any moist area a breeding ground for bacteria and odors. Like the guy said the only solution is disinfectant sprays to kill the bacterial problem. If you live in the southeastern US or any other hot and humid climate, this will be a regular thing.

The moisture comes from the evaporator actually freezing during operation then thawing after the car is shut off. If you turn the AC off a few moments before you reach your destination the water will be allowed to drain from the car.
High humidity areas are more likely to have this issue.

Why would draining be more effective with the car running than with the car shut-off?

Turning the A/C compressor off while leaving the fan on for a minute before shutting off the engine provides two benifits. It allows any ice that had formed on coil to melt off, and also the fan blows any water collected in the fins of the evaporator coil to be blown out lowering the chance of mold growth.

This same thing happens in my VW Beetle, only mine smells like vomit or stinky feet. It's really gross. I'm glad I read this thread because now I have some ideas.

The ice will melt off and drain, with or without the fan being on.

I do agree that the fan will certainly help to dry off the evaporator fins.