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How to Avoid the Dreaded A/C Mold/Mildew Smell

18953 Views 30 Replies 13 Participants Last post by  sailurman
I have heard from some car guys that the best way to avoid this is to never run in recirculate mode and always run fresh air inside... This is what I have always done on my 2000 Silverado and it it has 213,000 mildew free miles, but the Cruze seems to get the mildew smell more from fresh air on then in recirculate, maybe i'm wrong, what do you guys think?? My 2012 eco had the Mildew smell even after Dealer service/afterblow on didn't help, just trying to keep the smell from entering my pristine 2012 Ltz...
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The LTZ auto climate control pretty much does what it wants to control in-car humidity. It would not surprise me if it's running the AC in the winter and/or recirculate mode at times.
It doesn't matter if you run recirc or fresh air. It only takes a little mold/mildew to get the process started and once started the only way to get rid of it is to fumigate the HVAC ducting. Also, the dealership should turn on the HVAC after-blow to dry the ducting after you turn off the car.
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It doesn't matter if you run recirc or fresh air.
The OP is right - generally keeping it in recirculate mildews it up much more quickly. Running fresh air on most cars and turning off the AC to dry out the core ~2-5 minutes before shutting down the car will help keep it from forming on a soggy evaporator core that's just sitting around without airflow.

There are cans of foamy stuff you can spray up the drain hose under the car to clean off the cores - I think I'll have to do it to both cars in the spring. They're both ~2 years old and both have a little funky smell on defrost.
The OP is right - generally keeping it in recirculate mildews it up much more quickly. Running fresh air on most cars and turning off the AC to dry out the core ~2-5 minutes before shutting down the car will help keep it from forming on a soggy evaporator core that's just sitting around without airflow.

There are cans of foamy stuff you can spray up the drain hose under the car to clean off the cores - I think I'll have to do it to both cars in the spring. They're both ~2 years old and both have a little funky smell on defrost.
I just accuse my wife of having stinky feet (wink,wink)!
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Stinker Stinker , now you really know what is smelling up yer brand new car .
I believe if you run the A/C temp dial to maximum mode the car goes into recirculate without lighting the recirc lamp.

So, once at a decent level of temp I rotate it back.....you can feel a detent btw, and leave it there......I'm confident this is the case cause the fan quiets down as it it begins to pull outside only air.

And definitly get the afterblow enabled if you havent yet.....kind of weird the way it works/cycles/times on/off several times over a one hour period.

Rob
The best thing I've heard to do, whether you use recirculated air or not, is to shut off the A/C and let ambient air run through the system a few minutes before parking. I usually shut my A/C off when I'm at the end of the block on my home and never had a mildew smell in any cars.
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I believe if you run the A/C temp dial to maximum mode the car goes into recirculate without lighting the recirc lamp.

So, once at a decent level of temp I rotate it back.....you can feel a detent btw, and leave it there......I'm confident this is the case cause the fan quiets down as it it begins to pull outside only air.

And definitly get the afterblow enabled if you havent yet.....kind of weird the way it works/cycles/times on/off several times over a one hour period.

Rob
I also have reason to believe A/C is on(in warmer temps where the compressor is not locked out) when you hit defrost button but does not light up or show up on the touch screen.

As for recirc, it still lets in outside air just not as much as regular mode.
If you park your vehicle with a soaking wet evaporator in particular in a warm climate climate, nature will take over for developing mold. Not a new problem, started way back in the 50's when AC first became popular. Was a 1939 Packard as the very first vehicle that had AC.

Only way to prevent this is to switch the compressor off, my rule is about five minutes to leave the blower motor run at full blast before parking your vehicle. And have been doing this in the early 60's without any mold problems.

But mold problems is just the start of your problems, will also have corrosion problems. $$$$$ is the only result of these.

When automatic climate control first came out in around the early 60's, did not have a so called "Econ" mode, all it would do is switch off the compressor. So on these, mounted a rocker switch under the lower dash in series with the compressor clutch solenoid so I could switch it off. Didn't have to do with when they finally added on the Econ switch.

GM is very well aware of this problem, on just a hand full of vehicles, added a timer to keep the blower motor running for about five minutes after the ignition was switched off.

What is really downright stupid is switching on the AC with Defrost, at these colder temperatures, the moisture is very low, and switching on the compressor with a very cold compressor seal that is stiff, so you would lose refrigerant. Idiots that designed the Cruze did this exact same thing, even though they added a compressor switch. You can see that green light come on, but only when the ambient temperature is above about 34*F.

Not quite as bad with the V-5 compressor as it runs all the time, but when the cycling system was used, another POS, compressor would cycle on and off continuously accelerating from zero to the engine speed putting huge unnecessary stress on the belt drive system wearing it out with very little affect on defrosting your windshield.

On previous vehicles using a real mode switch, could cut the wire off that runs the compressor, but can't do this on the Cruze without having the source code on the BCM. So I just crack open a window the defrost the windshield almost instantly. Below 34*F, no problem, a thermistor keeps the compressor off.

Yet another problem finally solved with the Cruze is adding a cabin filter. Would describe the squirrel cage blower wheel as a leaf chopper that would pile up debris on the face of the evaporator and plug the drain hose. In these cases, the evaporator is sitting in a pool of water. Normally just removing the blower motor would give access to the evaporator so you could clean it out.

Slightly off topic, but can have the same exact problem with the HVAC system in your home, when the AC kicks off, so does the blower leaving the evaporator soaking wet for mold buildup. Solved this by modifying the furnace so the blower is always running at a low speed. Not only prevents mold buildup on the evaporator, but the entire house as well. Did this back in 1965 with my first HVAC system installation. With my newest furnace, low speed was running too high, so designed a motor control circuit to slow it down. Also keeps your home with a much fresher odor.

This is what is called common sense, that is becoming rare nowadays. And since that motor is always running, its the start up that really wears them out. Still kept my 30 year old blower motor, and still runs and looks like new.
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I also have reason to believe A/C is on(in warmer temps where the compressor is not locked out) when you hit defrost button but does not light up or show up on the touch screen.

As for recirc, it still lets in outside air just not as much as regular mode.
You are correct......the compressor will run in the defrost position with no lamp illuminated......this is so the humidity is drawn out of the air before it enters the cabin.
Nothing specific to the Cruze.....for the most part the way its been done for over twenty years.

Rob
I believe if you run the A/C temp dial to maximum mode the car goes into recirculate without lighting the recirc lamp.

So, once at a decent level of temp I rotate it back.....you can feel a detent btw, and leave it there......I'm confident this is the case cause the fan quiets down as it it begins to pull outside only air.

And definitly get the afterblow enabled if you havent yet.....kind of weird the way it works/cycles/times on/off several times over a one hour period.

Rob

what exactly is the afterblow and whats needed to toggle this on or off?
Afterblow turns the HVAC blower on and off after you turn the car off. It starts about 15 minutes after shutdown and continues for about an hour. There is BCM flag that needs to be set to turn it on. It makes the whine many of us hear after turning our cars off sound like nothing. Afterblow is loud. It can also drain your battery so if your car spends a lot of time driving very short distances you don't want to turn it on.
i do mostly city short trips so good to know is there a way to prevent the smell for someone like me who cant turn that on?
Define short. If the engine reached temperature you're probably ok with the power drain from after blow.
Define short. If the engine reached temperature you're probably ok with the power drain from after blow.


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I live about 5 min from work
I don't think 5 minutes is enouph running time for the afterblow to be enabled......

I don't have the update......actually, don't remember where I placed it.....but memory says A/C run time had to exceed 15 minutes before afterblow would cycle after shutoff.......for some reason, I think I posted it.

Rob
I have the ltz but I turn off the ac in the winter even tho on auto mode it turns out on should only be an issue in the summer when I want ac tho right

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The moisture only forms on the evaporator core in warm humid weather......winter A/C operation will not make mold cause the evap isn't wet.

Rob
The moisture only forms on the evaporator core in warm humid weather......winter A/C operation will not make mold cause the evap isn't wet.

Rob


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Right and since I use the compressor in the summer I should not get the smell either right
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