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Discussion Starter · #1 ·
So I've got a musty smell coming from my AC vents. It usually goes away after a little while but it stinks pretty bad. This is a problem I've experienced in other cars in addition to my MDX (which is a 2018 hybrid advance, fwiw). I've read online that the culprit could be the cabin air filter (which is called a dust and pollen filter in the owners manual), or it could be something having to do with evaporator coils and AC drain.

I've got a new cabin filter coming from Amazon this week and I'll swap that out myself, but I have a feeling this won't cure the issue. Does anyone know if there's an easy fix for the evaporator/drain issue? I'd like to avoid a trip to the dealer because I have a feeling this won't be covered by my warranty.

Thanks for any help with this.
 

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It could be from a dirty cabin air filter, clogged A/C drain hose, and/or dirty A/C system inside the dash. Same issue we all had with current and previous Acura's and Honda's. I'm lucky to live in low humidity of the southwest of single and teens humidity % on most days. The dealership will just do like any car A/C service place would do and spray disinfectant inside the A/C coils and, check the drains, and replace the cabin filter. Some MDX owners have to run the heater on really humid days to dry out the condensation on the coils before turning off the MDX.

I've always had good luck with FRAM Fresh Breeze cabin air filter with arm & hammer baking soda and activated charcoal. Recently switched to Bosch 6029c HEPA cabin air filters because of the wife's allergies. I always replace with new before spring pollen season.
 

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Discussion Starter · #4 ·
AC condensate drain tube
Thanks. Where do I find that drain? Guessing I should just run the AC and see where it's dripping from?

I saw a youtube video where you run a tube up through that drain and then spray some disinfectant foam up into the evaporator to clear away bacteria and eliminate the odor.
 

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If the drain isn't completely plugged you can look for the drip. I don't know where the MDX drain tube is, but in general they are behind the firewall (passenger compartment) usually on the passenger side. look for a soft rubber hose with an open end. Now if you have a sunroof often there are drain tubes for the sunroof as well, but those drain tubes generally exit real close to the A and C pillars, while the AC drain tube is usually somewhat centered in the passenger front seat width.
 

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Discussion Starter · #6 ·
If the drain isn't completely plugged you can look for the drip. I don't know where the MDX drain tube is, but in general they are behind the firewall (passenger compartment) usually on the passenger side. look for a soft rubber hose with an open end. Now if you have a sunroof often there are drain tubes for the sunroof as well, but those drain tubes generally exit real close to the A and C pillars, while the AC drain tube is usually somewhat centered in the passenger front seat width.
thanks will check this out tonight
 

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Replace cabin dust and pollen filter first. If the smell doesn't go away, use my following video for Second gen (should be similar for third) to clean your evaporator core, it's pretty straightforward and requires no experience:

Good luck!
 

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I agree to start with the cabin filter, which is super easy to change. From your posts it sounds as if yours might've never been replaced unless you had the dealer do it at some point. These filters can get surprisingly dirty - i.e. they do a pretty good job of filtering the air.

An a/c drain could be an issue. At a minimum, after you drive it with the a/c on and park it check under the vehicle a few minutes later to see if there's water on the ground. If there isn't then the drain might be clogged. One data point - my 9 year old 2014 MDX has not had a clog and never has a musty smell but I live in generally dry climate and it rarely rains here.

Another possibility - check the engine air filter box and on top of the engine cover for signs of rodents who may have decided to move in - especially if you leave it parked outside. You'll already be checking the cabin filter area for it. Look for nesting material and droppings. I've had rodents move into my cars multiple times and need to keep after them. The rodents can cause a musty and awful smell.
 

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So I've got a musty smell coming from my AC vents. It usually goes away after a little while but it stinks pretty bad. This is a problem I've experienced in other cars in addition to my MDX (which is a 2018 hybrid advance, fwiw). I've read online that the culprit could be the cabin air filter (which is called a dust and pollen filter in the owners manual), or it could be something having to do with evaporator coils and AC drain.

I've got a new cabin filter coming from Amazon this week and I'll swap that out myself, but I have a feeling this won't cure the issue. Does anyone know if there's an easy fix for the evaporator/drain issue? I'd like to avoid a trip to the dealer because I have a feeling this won't be covered by my warranty.

Thanks for any help with this.
Or a dead mouse. Had one in my 18 mdx. Smelled like a Subaru. Found the little beggar near the cabin filter but had to use my endoscope to pinpoint the location. Big treat to be rid of stinker.
 
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