The Mysterious Case of the Urinous AC

Hey fellas! This is Johanna in Mesa, AZ. I have kind of a strangely inexplicable phenomenon that occurs every time I turn the AC on high. The air it blasts smells strongly of URINE, but as it only lasts for the first 30 seconds or so, I’ve ignored it for the 5 years I’ve owned the car. What can I say - I’m a frugal woman, and a brief odor is hardly cause enough to take my car in to get looked at. However, I have only had the car in Arizona for the last 5 months (I was in Missouri previously), and as it is the desert (with temperatures hovering steadily at a toasty 105 degrees during the summer), I found myself smelling the odorous fumes with more frequency than ever before.

Other facts:
The smell does not accompany the air from the vents when I only have the fan running - just when I turn the dial to AC.
The car was salvaged (this has led to some morbid trains of thought).
The AC does not work all that well.

Any ideas on what might be the cause of my pungent predicament?

Thanks, guys!


mold or mildew.
More common in the higher humidity areas like Missouri but possible all the time.

When you turn off the car after using A/C, the evaporator core sits there a while defrosting. the resulting water drips out through a drain port on to the ground ( you may have noticed your car peeing under the passenger side just below the windshield/fender )

The longer it sits wet before drying, the more it mildews.

A/C shops have some stuff they use that’s a strong chemical, not just a deodorant, to get the mildew or mold off of the evaporator core. ( so strong they use mask and gloves when applying it )

Hmm hard to believe the mildew could survive in these super dry deserty conditions though. Maybe it’s dead and dried up, but the moisture re-wets it so it’s smelly. Smelly dead mold or mildew?
But then - there’s the fact that it goes away after about 20-30 seconds. Why wouldn’t it always smell if mold/mildew is ever present?

But your AC system isn’t super dry though. It gets wet every time you run the car’s AC. And mildew is good at surviving in those damp dark conditions.

Anyway, it could be smelling bad only at startup because there isn’t a whole lot of it, so it takes a while to build up the smell, so you only notice it then. Its also worth mentioning that your AC drain might be plugged, which allows more than usual amounts of water to stick around.

Sounds like that could be it. Guess I’ll check into how much it might cost to get an AC shop to take care of it. Thanks Ken and Malraux!

Before going to the professionals, you ought to try some simple remedies. I use Pine-Sol myself, but there is supposed to be a better product available called Ozium:

I’ve never used it but it is well-regarded. Or use a combination of the two. Before starting your engine, squirt some into the fresh air intake. This is through the slots in the cowl, under the wipers. You don’t even have to lift the hood. Let us know the results.

Maybe a stray cat sprayed the hood of the car.

No mention of make or model. Models with Interior air filters get contaminated and need to be replaced.

You know it’s funny that people ignore the interiors of their cars and yet actually live in numbers of days in them just driving.

It’s in the tag of the original post - Ford ZX2.
Would a cat spray last for five years? I might invest in that Ozium stuff. I’ve heard many good things about it too.

If you can get Ozium at your local hardware store, I’d suggest trying it too. It’s a Hospital-grade air sanitizer, so it’s some pretty powerful stuff. I used to carry a can of it on the road when I drove trucks professionally.

I recently had a friend at work have the same problem with her Camry. My advise was to replace the cabin air filter and shoot a load of Lysol into the filter box when the filter was out. She did just this, and hasn’t had a bad odor since. Cost her all of $15 for a filter and 25 mins. time. Filter was behind the glove box, but only needed a screwdriver to get to.

Escorts have never had a cabin air filter.
But I wonder if you’ve ever had a mouse in there ?