funked cabin air filter? changing it help? car washes, actually the nasty reclaim water they use, can make the inside smell like a$$ when it gets in the cabin air filter and then molds...solution for car wash types is to always press the recirc button so that nasty moist air is not drawn thru the cabin air filter from outside....

 

Cabin or whats called the ac filter was the first thing I tried. Also cleaned whole interior and removed debris in engine compartment near the windshield vents. It seems to happen mostly at first start up of The day, but not always . ?

 

Sometimes turning off the AC it will have a fowl odor until the AC kicks in and clean out vents. If you leave the AC on and never turn it off you should never smell it.

 

Just happened to my 17 after I washed it at a self serve car wash. Vacuumed out the interior, washed off the road salt, opened the door to leave and bam.

Side note. I had a 2016 Chevy SS that had AC odors. The dealer enabled what they called after blow. Essentially the fan would run for a predetermined amount of time after you shut off the AC compressor. I believe it was to help remove moisture from the duct work.

 

Do you have a Diesel? The emission controls on the Diesels use Urea to reduce the NOx in the exhaust, it can make some barnyard smells.

If you have gasoline, the AC collects a lot of moisture, check your drain to make sure the moisture is draining. Moisture and darkness is perfect for growing smelly bacteria. That could be the source of the smell.

I have turned the HVAC system fan on high, outside air and sprayed Lysol into the intake for the HVAC at the cowling at the base of the windshield. It would help to have the HVAC filter out, so it doesn't catch the Lysol and lets it circulate through the entire system. Do that several times over several days, using different modes, so it circulate to different parts to the system. May need to repeat over several days.

Then get a new cabin filter, the ones that are activated charcoal impregnated really help to kill odors.

 

FrigiFresh is what dealers tend to use to clear up anything from the A/C system.
As noted, pulling the cabin filter is recommended to allow really getting the cleaner down into the system good. Drain check, etc, and even having a mech do a complete flush of the thing may be needed if really bad, as crud gets in there and is good breeding ground for mildew, molds, etc.
However, A/C gunk usually smells more like stale sweatsocks, rotten straw, not barnyard.

I'd suspect Urea as most have noted if it smells like stale barnyard.

You can always remember the old rancher's saying "smells like money"

 

Maybe its the urea system , but it shouldn't be noticeable inside the cab.

 

Maybe it's the urea system. But it shouldn't be coming inside the cab. And I never smell it outside.

 

And you have a Diesel, cause if you have a gasoline engine it couldn't be Urea, there is no Urea used on gasoline engines.

I can get scents from the exhaust on cold start of my gasoline motor, if the vehicle is sitting still for more than a few seconds just after starting cold, the motor runs rich cold and you "can" smell it in the exhaust that just enough makes it into the cabin. Not a barnyard smell, with a cold gasoline motor you get that hydrocarbon smell, like taking a whiff of an open engine oil bottle, cause it is unburnt hydrocarbons coming out of the exhaust while its cold.

The Urea probably is just foul enough after a cold start, that tiny bit of scent making it into the cabin is noticeable.