CX-9 has musty mold smell when A/C runs and tried everything to fix

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2012 Mazda CX9 Touring
My wife's 2012 CX-9 has a musty mold like smell whenever her A/C kicks on. We bought it Certified Pre-Owned in 2014 with 44k miles and it didn't do it then. It has been doing it for the last 2 years and she's sick of it.

I've gone to the following projects to solve the problem with no success.

1) I've ran Lysol through the HAVC system.

2) I've had the vents professionally cleaned by a detail company with vacuums and vent dusters.

3) I've removed the glove box to inspect the white plastic basins under and to the left of the blower to inspect for excessive (or any) fluids and found nothing. I also found pure white translucency when holding a LED flashlight up to it to inspect for possible mold/mildew growth.

4) I've jacked up the car and hooked a shop vac up to he AC evaporator drain. No fluids or gunk were removed.

5) The cabin filter is pristine.

Any suggestions? It is to the point she wants to sell the car because of this issue. I smell it too and it is gross.

Thanks,
Steve
 

GJ-Molestor

Banned
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2011 BMW 528i, 2015 Mazda 6, 1995 Nissan Maxima Manual
My wife's 2012 CX-9 has a musty mold like smell whenever her A/C kicks on. We bought it Certified Pre-Owned in 2014 with 44k miles and it didn't do it then. It has been doing it for the last 2 years and she's sick of it.

I've gone to the following projects to solve the problem with no success.

1) I've ran Lysol through the HAVC system.

2) I've had the vents professionally cleaned by a detail company with vacuums and vent dusters.

3) I've removed the glove box to inspect the white plastic basins under and to the left of the blower to inspect for excessive (or any) fluids and found nothing. I also found pure white translucency when holding a LED flashlight up to it to inspect for possible mold/mildew growth.

4) I've jacked up the car and hooked a shop vac up to he AC evaporator drain. No fluids or gunk were removed.

5) The cabin filter is pristine.

Any suggestions? It is to the point she wants to sell the car because of this issue. I smell it too and it is gross.

Thanks,
Steve

I guess you're just gonna have to keep looking through the whole system for the source of the smell. It'll be there somewhere...
 
How many miles on it? Have you checked the vents outside of the car? Does it smell when the ac is recirculating air? Do you have a moon roof? Is the car parked outside or in a garage? How often does she run the heater? Are the floors damp? I'm asking a bunch of random ass questions because you might not have just a problem with the ac.
 
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2012 Mazda CX9 Touring
82k miles. Inspected exterior intake vents. Smells primarily when A/C is on with and without recirculating on. We have a moon roof but no oder comes from it and it is a good seal. Park inside every day. Heater runs often since we live in Wisconsin. Floors are not damp. Smell is still present even a year after I made my original post.
 
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2012 Mazda CX9 Touring
We've taken it to a dealer to have a foaming cleanser service performed. I've also done two of my own applications just like the dealer did, via the blower fan area that leads into the HVAC system behind the center console. I've also applied foaming cleanser through the top center console vents so that it drops down onto the condenser unit, after looking at how the CX-9 is put together on a schematic. That way I'm attacking they HVAC system in both directions. No gunk comes out of the drain under the car, just foam cleanser. Once the foam settles, it just looks like clear liquid.
 
I had a similar problem with my Mazda 3 and it ended up being the carpet and floor mats. Water was getting underneath the floor mats causing the carpet to smell. I sprayed the mats and carpet with peroxide, then put down a little baking soda, then sprayed vinegar, then used a mini green machine and hot water/vinegar mix. I also ran a fan over night to help with drying. The car smelled like a pickle for about 4 hours, but It killed the mold smell.
I asked about the moon roof because the drains can get clogged, causing water to back up into the car causing moldy smells as well. I'm sorry you're having issues and hope you get rid of the smell.
 
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13' CX-5 and 16' Mazda6 both Touring w/Tech/Bose
We've taken it to a dealer to have a foaming cleanser service performed. I've also done two of my own applications just like the dealer did, via the blower fan area that leads into the HVAC system behind the center console. I've also applied foaming cleanser through the top center console vents so that it drops down onto the condenser unit, after looking at how the CX-9 is put together on a schematic. That way I'm attacking they HVAC system in both directions. No gunk comes out of the drain under the car, just foam cleanser. Once the foam settles, it just looks like clear liquid.

What was the outcome 1 month later?
 
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Mazda CX-9 GS AWD
We have a 2010 GS with sunroof.
My wife also complained about musty smell over the winter in ours. I pulled the carpet up on drivers side and lots of water was underneath. Underpad was soaked. I am still looking for the source. A/C drain was OK, I couldn't really find the sunroof drain holes, but will look again. Check under your carpets.
 
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2016.5 CX-5 GT
My wife's 2012 CX-9 has a musty mold like smell whenever her A/C kicks on. We bought it Certified Pre-Owned in 2014 with 44k miles and it didn't do it then. It has been doing it for the last 2 years and she's sick of it.

I've gone to the following projects to solve the problem with no success.

1) I've ran Lysol through the HAVC system.

2) I've had the vents professionally cleaned by a detail company with vacuums and vent dusters.

3) I've removed the glove box to inspect the white plastic basins under and to the left of the blower to inspect for excessive (or any) fluids and found nothing. I also found pure white translucency when holding a LED flashlight up to it to inspect for possible mold/mildew growth.

4) I've jacked up the car and hooked a shop vac up to he AC evaporator drain. No fluids or gunk were removed.

5) The cabin filter is pristine.

Any suggestions? It is to the point she wants to sell the car because of this issue. I smell it too and it is gross.

Thanks,
Steve

most likely culprit is mold and mildew growing on the evaporator coils where the airflow blows across, thus the musty smell in the cabin, only way to get rid of it it to kill the smell at the source (the coils) ; air fresheners and Lysol only mask the problem.

there are some new products that you bacially run the HVAC system in full blast and fog the cabin with all the doors and windows closed for like 10 miunutes without anyone in the car ; so the fog will go across the coils and kill the micro-organisms

https://www.amazon.com/Turtle-Wax-50819-Odor-X-Kinetic/dp/B077JXS4Q6/ref=pd_bxgy_263_img_3/141-6847731-2853123?_encoding=UTF8&pd_rd_i=B077JXS4Q6&pd_rd_r=973bcedc-8170-11e9-b06b-1967775fe31c&pd_rd_w=28RsH&pd_rd_wg=5OdBZ&pf_rd_p=a2006322-0bc0-4db9-a08e-d168c18ce6f0&pf_rd_r=415XKZ7SB2NYFYQ3306A&psc=1&refRID=415XKZ7SB2NYFYQ3306A
https://www.amazon.com/Meguiars-Whole-Refresher-Odor-Eliminator/dp/B00G49DVGG/ref=pd_bxgy_263_img_3/141-6847731-2853123?_encoding=UTF8&pd_rd_i=B00G49DVGG&pd_rd_r=91666dce-8170-11e9-bbb8-afc81129452f&pd_rd_w=1hXdO&pd_rd_wg=mh2e9&pf_rd_p=a2006322-0bc0-4db9-a08e-d168c18ce6f0&pf_rd_r=0R6YG4XB6VJNYDPNS9CF&psc=1&refRID=0R6YG4XB6VJNYDPNS9CF

or you can go the more direct route and find the drain tube and foam the whole evaporator core and let the foam kill the mold and mildew and let it drip out of the condensation drain, sorry I only know the location for the CX-5 but CX-9 may be similar, another way to get to the core is to remove the glove box and the fan blower housing and insert the foamer tube from there for direct access to the evap core.

https://www.mazdas247.com/forum/showthread.php?123856340-Unclog-a-c-drain-and-remove-musty-smell-easily&highlight=musty

or another option is the remove the air filter and let the blower blow foam across the coils as in this video, you feed the air filter cavity as the blower draws the foam across the coils

https://www.amazon.com/gp/product/B0002Z2MKO/ref=ppx_yo_dt_b_asin_title_o02_s00?ie=UTF8&psc=1

 
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2007 Mazda CX-9 Touring
I saw this post and i would like to ask a question. Whenever i replace my cabin air filter the old one has leaves on it. Is this normal? What part of the car do the leaves get in from.
 
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2019 Mazda CX-9 Signature, Machine Grey Metallic
I had this issue on all the vehicles that I*ve owned. It really is caused by the condensation from the AC that doesn*t get to dry out completely. I used Klima Cleaner which works but requires quite a bit or work to use.

The one I currently use, and has been quite effective, is the Enerzen Commercial Ozone Generator. It*s easy to use and makes the entire interior smell fresh afterwards. After treating the car, I make it a habit of turning off the AC about a mile or so away from my destination so that the AC gets a bit of chance to dry out. I have 3 vehicles and I*ve used it on all of them with the same results.
 
We've taken it to a dealer to have a foaming cleanser service performed. I've also done two of my own applications just like the dealer did, via the blower fan area that leads into the HVAC system behind the center console. I've also applied foaming cleanser through the top center console vents so that it drops down onto the condenser unit, after looking at how the CX-9 is put together on a schematic. That way I'm attacking they HVAC system in both directions. No gunk comes out of the drain under the car, just foam cleanser. Once the foam settles, it just looks like clear liquid.

STEVE I HAD A 2004 LEXUS WITH THE SAME PROBLEM. THE CAR HAD A MOONROOF. SOMEONE TOLD ME THERE WERE WEEP HOLES IN THE FRONT OF THE TRACKS THAT RUN DOWN THE SIDES BEHIND THE RIGHT AND LEFT AREA WHERE YOU PUT YOUR FEET. STAY WITH ME STEVE. THE TUBES CARRYING THE WATER DOWN BOTH EMPTIED INTO A COMMON AREA BEHIND THE RIGHT AND LEFT WHEEL WELL. THAT AREA WAS CLOGGED WITH LEAVES. I LIFTED THE RUG WHICH HAD AND UNDER PADDING MADE OF JUTE THAT WAS WHERE THE SMELL WAS COMING FROM. SOOOOO I WOULD START THERE. LIFT THE RUG (NOT HARD TO DO) AND SMELL THE JUTE. IF IT SMELLS YOU FOUND PART OF THE PROBLEM. IF YOU HAVE THOSE WEEP HOLES LIKE I DID, I STUCK A 12 GAUGE STRANDED WIRE INTO THE HOLES TO CLEAR THEM. THE BIG SURPRISE WAS WHEN I REMOVED THE PLASTIC WHEEL WELL COVERS. THEY WERE PACKED WITH LEAVES SORRY FOR THE CAPS, NAM VET BAD EYES. GOOD LUCK
 
WHEN YOU ARE NOT ON RECIRCULATE, YOU TAKE IN OUTSIDE AIR. THE AIR COMES IN THROUGH AN OUTSIDE VENT WHICH SOMETIMES WILL ALSO BRING IN BITS AND PIECES OF LEAVES.
TADAH
 
We have a 2010 GS with sunroof.
My wife also complained about musty smell over the winter in ours. I pulled the carpet up on drivers side and lots of water was underneath. Underpad was soaked. I am still looking for the source. A/C drain was OK, I couldn't really find the sunroof drain holes, but will look again. Check under your carpets.
SEE MY LATER REPLY IT'S ALL IN CAPS. GOOD LUCK
 
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2011 CX-9 GT AWD
Since i cleaned HVAC system with foam cleaner, I have no any smell.

opt1: (i used)I applied it from the drain tube. remove the kick panel on right hand side of the gas pedal then unplugged the drain tube. sprayed entire bottle of foam cleaner then plugged the drain tube back. installed new cabin filter and no more smell.

opt2: push the sprayers pipe in to the center air vent then spray entire bottle then wait 15 min. replace cabin filter.

opt3: remove blower fan and spray entire bottle in to the evaporator or remove cabin filter then push pipe in to the evaporator between fins of blower fan. replace cabin filter.

I used nextzett 96110515 Klima-Cleaner

It has instruction on the bottle.
 
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