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Q: Moldy smell from AC at startup

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I've seen lots of post on forums and websites about potential condensation collecting inside the ducting that is harboring microbial growth which is producing that smell.

Now my question is, why don't I smell it when I keep the AC off and ramp up the fan? This question may lead to the following: how do I find where the source is? Is the only way to thoroughly clean out this mess by taking the ducting/trunking out and clean/soak? Is it doable? I'm skeptical about those off-the-shelf sprays. I'm looking for a solution that doesn't just mask over the problem but getting rid of the problem for good. What are your views?

Hello, thank you for writing in. The best way to remove a moldy smell from your vehicle’s air conditioning system is to replace the evaporator. This is a very time consuming and expensive repair, but is the only way to fully remove the mold. I would recommend enlisting in the assistance of a certified professional to have the evaporator replaced as the dash must be removed in most cases. This could result in many screws and bolts missing or in the wrong place. It is also important that the air conditioning system is evacuated prior to replacing the evaporator to ensure that no refrigerant is released into the atmosphere. If you find that the mold is at a more reachable place, you may be able to get rid of it on your own. Here at YourMechanic, we can have a technician come to your home or office to inspect this smell for you, and make or suggest the necessary repairs.

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