By
daniel0269, November 15, 2014
Hi all,
Sometimes when temperatures go down I switch to the white or red when I do that a horrible smell comes out. This only happens when the car is already running, and if I make the switch of temperature otherwise no odor will come out. Moreover, if I switch the temperature before the car starts the odor wont come out. Any thoughts of what might be causing this odor.
Any input is valuable thank you
What year is your Corolla? If it has a cabin air filter, was it cleaned or replaced lately?
Sorry it is a 2001 Corolla it doesn't have cabin filter
Possible that there is mold/mildew infesting your blower unit and internal A/C element. If the car sat for some time, possible some critters have made a home inside the blower, cowl area, any place up under the dash.
Since this happens when the car is running and you switch temperatures - means that this source of odor is coming from the blend door in the system. Need to do some additional investigating - start from the cowl, remove any debris you see, move to the cabin, especially around the blower assembly. No cabin air filter in this generation - so there are times where I find a bunch of debris in my blower assembly. I believe the blend door is on the passenger side - but it has been some time since I played around with that.
If everything looks clear - then you're left with pulling the rest of the duct work apart or using a spray deodorizer and hosing down the entire system.
Last year my car navigated across a flood area the water was over my knees so I'm guessing that might have had something to do with it. The funny thing is my car survived without a problem while BMW, Mercedez Benz, and some newer cars were all being picked up ^.^
Definitely. Pretty much have to pull everything apart, as any organic material you picked up in flood is festering somewhere in the car - mold mildew could be anywhere in there. You've pretty much got it isolated to the HVAC system - just depends on how much work you want to do.
Could just carry some of that HVAC deodorizing aerosols - most have a long flex tube that you can snake down into the ductwork - just hose the system repeatedly and hope for the best.
After a long time I think the problem have solved by itself lol 
