Why does my AC stink up my car?

Dear Car Talk

Dear Car Talk | Nov 01, 1989

Dear Tom and Ray:

When I turn on the air conditioner in my 1988 Ford Thunderbird, I get a musty, mildew odor. It goes away in about 5 or 10 minutes. What's my problem?

RAY: You have mold building up in your air conditioning system. One of the air conditioning components is something called an evaporator. The evaporator works by sweating like a glass of iced-tea in July. The air conditioning system makes the evaporator cold, and when the moist, hot air hits the evaporator, the moisture condenses and produces water. This condensation and removal of the moisture in the air is the "conditioning" in air conditioning.

TOM: But the water has to go somewhere. It's suppose to drain out through a hose that runs from the evaporator housing to the bottom of your car. In your Thunderbird, however, all of the water is not draining, and that's creating a perfect environment for mold to grow (dark, warm, and moist). It sort of like the inside of your gym bag, Rufus.

RAY: You may think it goes away in 5 or 10 minutes, but trust us, you're just getting used to it. Have you noticed that the last few times you've tried to pick up hitchhikers, they've refused the ride after opening the door?

TOM: You have two choices. Either have your mechanic unclog the drain so that the water can escape. It's a simple procedure, and if you remove the water, the mold will eventually die and the smell will go away. Alternatively, pour two cups of flour, an egg, and a teaspoon of vanilla into one of your AC vents. That won't kill the mold spores, but it will make the car smell like angel food cake for the next few weeks.

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