Funny Vent Odor
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Junior Member
Joined: Aug 2018
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Funny Vent Odor
Hey guys, I have a 2012 F150 XLT (bought used in 2015). Low miles, and no major problems at all. However if it's raining when I have the air conditioner running, I get an odor from the vents. It smells a lot like kitty litter. Within about 30 seconds the rain starting, I get hit in the face with this odor. As far as I know the 2012s do not have cabin filters, correct? I've sprayed some odor eliminator into the return air and in the cabin, but this has done very little. We have hot and humid days here, but the only time it happens is when it rains. It's been doing this for the past couple years or so, and I'm looking for any type of solution to it. Anybody else ever deal with anything like this? Thanks!
5 Year Member
Joined: Mar 2009
Posts: 1,321
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From: The Great Midwest, aka, Flyover Country
Hopefully, you don't have the dreaded mouse nest in the air box. If you routinely park outside, especially under trees or where organic debris can filter down into your cowl intake, it would be wise to pull the cowl covers off--a pretty easy task--and clean the bottom of your air box. It's amazing how much cr-p collects in the bottom, even though the cowl intake seems like it's pretty well screened.
5 Year Member
Joined: Jul 2018
Posts: 708
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From: NW Penna
Outside cabin air comes from cowl vent - the grid at the base of the windshield at the rear of the hood. Sometimes stuff can get in there and block the drain - also something that might stink when it gets wet. Being you said that the smell starts only when it starts raining I think this is a good place to start.
Hard to see in there. I’ve never had mine apart but did have the drain line clogged on my old Bronco II. My body shop guy showed me where it was at one end - I was able to use the blow gun on my air compressor to clear the drain.
As a test you could spray some water into the cowl vent and see if it fills up without draining - won’t hurt anything to try. Maybe it might help determine if something like a mouse nest is in there.
Other than that you might very well have a mouse nest in the duct somewhere - not fun to try to find or get to.
Another thing to try - you said it starts happening soon after it starts raining. As soon as you smell it next time hit the recirculating button and see if the smell stops. If it is something in the cowl like I said the smell should stop.
Hard to see in there. I’ve never had mine apart but did have the drain line clogged on my old Bronco II. My body shop guy showed me where it was at one end - I was able to use the blow gun on my air compressor to clear the drain.
As a test you could spray some water into the cowl vent and see if it fills up without draining - won’t hurt anything to try. Maybe it might help determine if something like a mouse nest is in there.
Other than that you might very well have a mouse nest in the duct somewhere - not fun to try to find or get to.
Another thing to try - you said it starts happening soon after it starts raining. As soon as you smell it next time hit the recirculating button and see if the smell stops. If it is something in the cowl like I said the smell should stop.
Senior Member
Joined: Jul 2016
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From: Central Minnesota
5 Year Member
Joined: Mar 2009
Posts: 1,321
Likes: 532
From: The Great Midwest, aka, Flyover Country
All the deodorizing in the world won't help permanently. Might stop it for awhile, but rotting organic material like leaves, seeds, pollen dust is gonna still smell when it gets wet.
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Joined: Dec 2016
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From: Midwest USA
Don't know what cat litter smells like and don't want to know.... but does the air smell fresh after 10 or so minutes?
If so,
its moisture growing mold in the HVAC system.
The Lysol treatment down the outside vent is in order.
Spray it into the vent with all windows/doors open, blower on high and if necessary heat on high.
If this fixes it permanently, then about 15 minutes or so before getting to your destination, turn the AC off and leave the blower on high to dry out moisture in the HVAC system
This IMO is important especially if you live in a humid climate.
I do that all the time and have no AC odors in any of my vehicles.
If the odor is persistent after the Lysol treatment, then as the others mentioned you've got mouse crap or something else rotting somewhere in the vent system.
Not a fun thing.
Do a search, there's a recent thread here on that subject.
If so,
its moisture growing mold in the HVAC system.
The Lysol treatment down the outside vent is in order.
Spray it into the vent with all windows/doors open, blower on high and if necessary heat on high.
If this fixes it permanently, then about 15 minutes or so before getting to your destination, turn the AC off and leave the blower on high to dry out moisture in the HVAC system
This IMO is important especially if you live in a humid climate.
I do that all the time and have no AC odors in any of my vehicles.
If the odor is persistent after the Lysol treatment, then as the others mentioned you've got mouse crap or something else rotting somewhere in the vent system.
Not a fun thing.
Do a search, there's a recent thread here on that subject.
