Has your car or truck's air conditioning system started to blow a pee smell through your car's air vents into the
cab?
That pee (or ammonia) smell is likely coming from a build-up of mold, mildew, and bacteria.
The mold generates ammonium, which urine also contains, which is what you're smelling.
The problem can usually be solved by spraying Lysol into the vehicle's cabin air intake while running with the AC on max settings.
Sometimes after the air conditioner has run for a bit and the system has cooled off, the pee smell is less
noticeable.
Woman smelling something like urine coming from car vents
Why Does Your Car's Air Conditioning System Smell Like Pee Or Cat Urine?
An essential part of a car's air conditioning system is the evaporator.
The evaporator is designed to remove any moisture from the air being cooled.
Ideally, this moisture dissipates or drains through the drain hole onto the ground.
Mold will accumulate if the drain hole is plugged or the moisture doesn't dissipate.
Luckily, the problem is often quite simple and cheap to fix, and you probably won't need a mechanic to
fix.
The collection of mold generates mycotoxins or byproducts, which frequently can be more dangerous than the mold
itself.
Mycotoxin Chemical Structure - www.commons.wikimedia.org
Dangers of Mycotoxins (Mold)
Mycotoxins are secondary metabolites produced by
microfungi that are capable of causing disease and death in humans and other animals. Because of their
pharmacological activity, some mycotoxins or mycotoxin derivatives have found use as antibiotics,
growth promotants, and other kinds of drugs; still others have been implicated as chemical warfare agents.
Quoted from: Bennett, J W,
and M Klich. "Mycotoxins." Clinical microbiology reviews vol. 16,3 (2003):497-516.
doi:10.1128/cmr.16.3.497-516.2003
If you believe the most likely culprit, mold, causes the smell, there are several solutions to fix the problem and
get your vehicle smelling like new again.
How Do You Get Urine Smell Out Of Car Vents?
There are several ways to fix a urine smell from car air conditioner vents.
The easy and quickest method is to use a disinfectant like Lysol and spray it into your car's air intake vents with
the car's ac system on high.
It is easy and usually effective.
Watch the video or read through to learn how!
Method #1: Use Lysol Or Similiar Disinfectant
Step 1) Drain Air Conditioner Condenser
The first thing to do is ensure that your air conditioner drain line is not plugged.
This is done by turning on your vehicle and the car's air conditioner and letting it idle in park.
After 5 or 10 minutes, look under the vehicle, and you should see your AC condenser dripping water onto the ground.
If you do not see water on the ground, you will need to unplug the drain line from the air conditioner unit and push
a wire through it until whatever is plugged comes unclogged.
Reattach the drain line and continue onto the next step to rid the car of odor.
Once confirmed that the air conditioner drain is not plugged, it's time to move on to the next step.
Step 2) Turn on the Car's Air Conditioner
Turn the car on, engage the AC, open all the vents, and turn the fan to its highest setting.
The recirculation setting must be turned off as you want the AC system drawing in air from the outside.
Step 3) Open your window
Don't forget to crack your window as you don't want the harmful Lysol fumes to affect you or your family.
Step 4) Spray Lysol into the air intake vents
Spray Lysol into cabin air intakes (indicated with red arrows) with AC on high drawing air from outside.
At the bottom of your windshield, there is a vent called the air intake vent on the outside of your vehicle.
With the AC running, you should feel suction at these vents.
Take a large can of Lysol and spray the whole can evenly on both the driver and passenger side while the vehicle and
AC are running.
Step 5) Let your car run for 10 minutes
Leave the vehicle running for ten minutes to let the Lysol fumes circulate through the AC system.
In most cases, this method should fix the problem and give you fresh air again from your air vents.
If the air conditioning system still blows a urine smell, you can move on to the following method.
Method #2: Clean Air Conditioning System
If Lysol doesn't fix the problem, another solution is using a specially formulated chemical made for cleaning AC
units.
This second method requires a bit more work than the first method but will clean any rust, oil, or debris of the AC
coils and disinfect the system.
Clean coils will make the system work more efficiently, improve cooling, and leave your car smelling awesome.
Step 1) Purchase an HVAC system cleaner
Make sure you purchase a can with an application tube you can slide up through the AC drain tube up to the AC unit.
Air conditioner cleaner kits can be purchased at your local hardware store or auto parts store.
Step 2) Apply cleaner to the AC unit
While the car is turned off, locate the drain tube on the AC compressor and spray an entire can of the cleaner foam
into the AC unit up through the drain tube.
Step 3) Let sit for 15 minutes
Pinch off the drain tube so the cleaner doesn't drain back out, and let the vehicle sit for 15 minutes, leaving the
car off.
Step 4) Let drain
Unpinch the drain tube, let the chemical cleaner drain out, and run the car to confirm the cooling system runs and
smells excellent.
If it doesn't work and you are sure that the chemical is reaching the inside of the AC unit, you may need to repeat
the process with a second can.
You can now also add a can of Lysol through the air intake vent like in Method #1.
If the car air conditioner smells like pee after going through these steps, you may have to get the air conditioning
system looked at by a professional as described in the following method.
Method #3: Get Your Car's AC System Looked At By A Mechanic
The last option would be to remove the evaporator and thoroughly clean it.
As you can imagine, this is quite difficult and time-consuming but may be necessary if neither of the previous
options works.
Most likely, this step would be better left to a professional.
Other Reasons Your Car Air Conditioner Smells Like Pee
Small animals, especially mice, will crawl into a vehicle's air intake system and nest.
As a result, mice's urine and feces can collect.
Before disinfecting, you have to disassemble the intake and clean out the intake by hand.
Be sure to wear gloves and a mask! Or better yet, leave it to a pro!
Natural Products That Remove Mold
Lysol is a tried and true remedy for mold in vehicle vents that you can't reach. However, if the mold can be reached by hand, you may want to try some more "natural" solutions to eliminate mold.
Read our post on how to get mold out of a car with everyday household products.
Car Smells Bad When AC Is On
When there is a bad odor coming from your AC, there are a couple of usual
suspects. Because moisture and other contaminants tend to build up in your
system, chances are that something needs cleaning or replacing.
Dirty Cabin Air Filter
Cabin air filters are designed to keep dust, mites, and other contaminants
out of your car’s air. These filters need to be replaced every so often;
roughly every 50,000 to 100,000 miles.
Mold and Mildew
Where moisture collects, bacteria, mold, and mildew can grow. Check your
AC’s evaporator, as this is the most likely collection point for the musty
smells that mold and mildew produce, though you may want to leave flushing
the system out to a professional.
Debris Buildup
Dust and debris can collect in your AC vents. A key sign of this problem is
a burning smell when you first turn on your vehicle. Tune-ups and
maintenance can usually fix this issue once you identify it.
Conclusion
If your car's air conditioner smells like pee, there are several different methods of differing complexity and time
that will fix the problem.
Start by troubleshooting the problem by ensuring that the problem is indeed the car air conditioner and not something
else.
Then after ensuring that the car air conditioner is the culprit, you can begin with method #1 and work your way down.