Rick's Free Auto Repair Advice

Car AC smells bad

Car AC smells bad

If your AC smells bad, you have mold/mildew growing in the evaporator coil. Some people hang a car freshener, but that won’t get to the root of the problem. Others spray Lysol into the recycle air intake, but that doesn’t get to the problem either. You need to clean the evaporator coil and coat it with special anti-mold treatment.

What causes the car AC smells bad condition?

R-134a isn’t as efficient as the older R-12 refrigerant. To get the same cooling power, car makers had to pack more cooling fins into the small evaporators in your dash. AC evaporator coils remove humidity from the air and the condensed water is supposed to drain off the fins. However, due to the dense pack of the fins, capillary action keeps some of that water clinging to the closely packed fins. After you shut down the AC, the water develops mold and mildew and that’s what causes the smell.

To make matters worse, the mold and mildew can develop slime that clogs the condensate drain tube. When that happens, the AC condensation can’t drain out of the evaportor box and instead drains onto your passenger carpet.

To make matters worse, many car owners don’t change their cabin air filters on time. A clogged cabin air filter reduces airflow and that prevents the evaporator coil fins from drying off completely, making the problem even worse

How to clean mold/mildew off the evaporator coil

Kool-it makes an antibacterial spray foam that not only knocks out the science experiment growing

Musty smell in car

Shoot evaporator cleaner disinfectant directly into the heater case to kill mold, mildew and coat the coil to prevent it from re-occurring

inside your dash, but also treats the evaporator coil to prevent it from happening again soon.

The manufacturer says that one treatment lasts a full year. I have no connections with the company, but I have used their product and it works well.

How to use Kool-IT

Locate the condensate drain tube

This is a DIY project. All you need to do is locate the AC condensate drain tube.

It’s usually located at the bottom of the heater box on the passenger side. It’s a black rubber tube. You’re going to remove it. But first, lay an old towel under it in case the drain tube is plugged. If it is, a lot of water may rush out of the drain when you remove it.

If water comes out, that means the drain tube was plugged. Once the water stops draining, clear out the drain tube using compressed air or a pipe cleaner.

Connect the tube from the can of Kool-IT

Next, connect the tube from the can of Kool-IT to the drain. Press the nozzle and load the entire can into the heater box.

The product will foam up and fill all the nooks and crannies in the evaporator fins. The antibacterial cleaner will kill and clean the evaporator. Follow the directions on how long to leave it in. Reconnect the drain tube and the foam will dissipate and the crud will flow out the drain tube.

Run your AC at full blast to dry out the evaporator coil. The treatment lasts about a year.

© 2012 Rick Muscoplat

Posted on by Rick Muscoplat

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