A couple of days ago, I noticed a very pungent, strong smell coming from my heat vents when I turn the heat on. The best way I can describe the scent is like cat urine.

Does anyone have any ideas on what is causing this smell?

 

mildew.

it's pretty much too late to do much at this point.
Once you start smelling mold, it never really goes away. You can do all the BG fridgifresh fridgiclean you want, but the smell will eventually come back.
Just spray lysol disinfectant into the vents to cover up the smell, and run the heat high to maybe kill some of the mold.

One thing you should not do is spray lysol from outside the windshield. That might have worked on older cars. But our intake beneath the cowl has a screen cover, which would soak up and waste all the lysol. Just spray from the interior vents. Or if you want to spray more upstream, remove the cabin filter, and spray through the slot in the glove compartment.

 

I hear when your heater core goes bad you experience a smell like this. Probably from the coolant leaking and sitting around in there.

Try taking it to the dealer if you have warranty.

 

Sounds to me like the smell of collected water in the evap core rots, very common with people who use the AC with the heater on or when ac is used but not allowed to dry the evap water. Best way to aviod this is to allow the air to run with ac off to allow it to dry before shutting off the car.

 

I'd try a new cabin filter before anything else. You might be surprised. Get the carbon impregnated one. I got the one for my IS from rockauto.com

 

I appreciate all of the responses. I actually did take my car into the dealership today and I dropped it off at noon and when I called this evening around 5:00, they said that they were still trying to find the source of the odor. I would think that this wouldn't be extremely difficult to diagnose this but apparently so.

I'll keep everyone updated on what the dealership finds out.

 

Make sure the evap water drain tube is clear and not clogged too, if the water doesn't drain to the floor it will cause the water to sit and rot which causes the urine-like odor.

 

Believe me you are not the only one with this NASTY DISGUSTING SMELL. Keep in mind it only happens when the heaters are on. In the summer with AC it smells like fresh flowers. It is mold and mildew build up. I am actually waiting on my $500 gift card from lexus to make an appointment and tackle this problem. Its horirble and nasty, keep us updated of what lexus has done to you to fix this problem!!!!!!!

 

I've found that parking my car with the moonroof tilted open and sliding cover open helps dry out the interior and takes away the smell over time. I also apply Lysol and keep max heat running for ~10 mins every few months, especially during warmer seasons (basically 9 months out of the year in CA).

 

I always shut my cars off with the A/C set to fresh and it definitely helps moisture escape from the system. Started doing this when my wife's SC had a strong smell the first summer after we got it. I did Lysol from the cowl and Ozium on the inside every day for a week and it's been fine since.

 

Well, the verdict is in and it's not mildew of any sort...they found a freakin' "mouse nest"! How disgusting is that?! They, of course, got rid of it and recommended that I replace the cabin filter, which I gladly had them do.

Looks like my next call is going to be to the exterminator!

 

HUH...................... Where did they find a mouse nest? More details please!!!!!!!

 

Baaaahahaha!!! That's crazy no wonder you were smelling urine your car prolly smelled like a dirty hamster!!!!

 

Where was the location of the mouse nest and through which orifice did they get in from?

 

It might be the coolant. Sometimes that is what causes the smell and it needs a flush.