Hey everyone, I’ve been having an issue with my car’s A/C. After I turn it on, there’s this musty, wet dog smell that comes and goes. I replaced the cabin filter a month ago, but when I checked it yesterday, it looked pretty rough. It was all soaked through with what looks like muddy water, and it smells just like the wet dog smell. My car is a 2018 Mazda 6 wagon (face-lifted model). The floors in the car aren’t wet though. Does anyone have any ideas on what’s going on or what I should do? Appreciate the help!
Yeah, it sucks in outside air, and I’ve found leaves and other stuff in there before. Maybe some water got in. Just replace it regularly and it should be fine.
Not sure, but did you make sure it was installed the right way? Could be that, or maybe something else happened? 
Bliss said:
Not sure, but did you make sure it was installed the right way? Could be that, or maybe something else happened?
The filter can only go in one way though 
Bliss said:
Not sure, but did you make sure it was installed the right way? Could be that, or maybe something else happened?
The filter can only go in one way though
I’ve actually seen people put it in wrong on Mazdas in this forum. Make sure the ‘up’ arrow is pointing the right way for most of them.
Do you hear a sloshing sound when you turn? If so, your drain tube might be clogged, and that could cause water to build up. You can pull back the carpet, pop out the plug and tube, and clean it with a pipe cleaner if needed.
@Vic
I don’t hear any sloshing, but I’ll check the drain tube tomorrow. Any idea where it’s located? I can’t find anything online about its location.
Usually that musty smell comes from mold on the A/C condenser. You can buy a foam spray that gets rid of mold, though I haven’t tested it myself. Or, you can take it to a shop that refills A/C systems—they can clean it for you, though they might charge extra for the foam spray.
@Steele
The musty smell seems to be coming from the cabin filter itself, though. The old filter didn’t have any smell or look soaked through like this one.
Bay said:
@Steele
The musty smell seems to be coming from the cabin filter itself, though. The old filter didn’t have any smell or look soaked through like this one.
In that case, maybe try pouring water around the area and see if you can find where it’s coming in. The filter gets soaked from outside air and rain, but it shouldn’t smell like that. Keep an eye out for any leaks around the filter.
Has it been snowing lately? With the heater or defrost on high and drawing fresh air, it could pull in some snow that melts onto the filter.
Kai said:
Has it been snowing lately? With the heater or defrost on high and drawing fresh air, it could pull in some snow that melts onto the filter.
There hasn’t been any snow here, but I wonder if pouring water on the windshield to de-ice could let some in through the fresh air intake? The filter is a muddy color, but it’s hard to get a good photo of it.
@Bay
If the fan’s on high with fresh air, it could pull in water that way too. The muddy color is probably from dust the filter trapped, and charcoal dust from the filter might add to that too.
You could try spraying some Lysol in the vents near the windshield.
Sage said:
You could try spraying some Lysol in the vents near the windshield.
They sell vent cleaners at auto parts stores, but Lysol or alcohol might leave a residue or even be a fire hazard. I’d stick to replacing the filter first and save the spray for later if needed.
Sage said:
You could try spraying some Lysol in the vents near the windshield.
It’s better to use a product specifically made for car HVAC systems, like BG’s FrigiFresh. It costs about $25 a can, and one can will last a while. It works great, and you can do it yourself. Your dealer would charge $100 for the same thing. To use it, spray it in the outside air intake near the passenger wiper blade for about 15 seconds while the A/C is on fresh air, then switch to recirculation and let it run for 10 minutes. I do it a few times a year. Also, check your blower motor—it’s a common problem with Mazdas and could be contributing to the smell. It’s an easy fix, and you can find plenty of YouTube videos for it. Sometimes a mouse can get in there too, but you’ll know if that happens because the smell is unforgettable. Wear gloves if you’re checking!