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Musty AC Smell & Weak Airflow in 2016 Mazda CX-9

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Mike T. · rep 0 · May 25, 3:36 AM · 1 replies · solved · Question

Vehicle: 2016 Mazda CX-9 Touring

Hey everyone, I've got a 2016 Mazda CX-9 Touring with about 80,000 miles, and the air conditioning has developed a really unpleasant musty, mildew-like smell, especially when I first turn it on. It eventually fades a bit, but it's pretty gross. Also, I feel like the airflow isn't as strong as it used to be, even on high fan settings.

I'm thinking it might be the cabin air filter, but I'm not sure if there's anything else I should be checking. Has anyone else experienced this with their CX-9? Any tips for getting rid of the smell and improving the airflow? I'm hoping it's a DIY fix!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 25, 3:36 AM

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ClearTheCode admin answer:

A musty smell from the AC and reduced airflow are classic symptoms pointing to issues within your climate control system, most commonly related to the cabin air filter and evaporator coil. This is a very common problem, especially in humid climates.

Here's a breakdown and steps to address it:

  1. Replace Cabin Air Filter:
    • Cause: This is the most likely culprit for both symptoms. A clogged cabin air filter restricts airflow and can trap moisture, dust, and allergens, leading to mildew growth and odor.
    • Procedure: The cabin air filter in your 2016 CX-9 is typically located behind the glove box. It's usually an easy DIY replacement. Refer to your owner's manual or an online video for specific instructions.
    • Frequency: It should be replaced every 15,000-20,000 miles or once a year, more frequently if you drive in dusty conditions.
  2. Clean Evaporator Coil:
    • Cause: The evaporator coil, located deep within the dashboard, gets cold and condenses moisture from the air. This damp, dark environment is perfect for mold and mildew growth, which causes the musty smell.
    • Procedure: After replacing the cabin filter, you can use an AC evaporator cleaner spray. These products are typically applied through the fresh air intake or directly into the evaporator drain tube. Follow the product instructions carefully. This helps kill bacteria and mold.
    • Tip: To help prevent future odors, run your fan on high with the AC off for a few minutes before reaching your destination. This helps dry out the evaporator coil.
  3. Check AC Drain Tube:
    • Cause: If the AC drain tube (which allows condensed water to exit the vehicle) becomes clogged, water can accumulate in the HVAC housing, leading to excessive moisture and odor.
    • Procedure: Look for water dripping under your car when the AC is running. If no water drips, the tube might be clogged. It’s usually accessible from underneath the car.
  4. When to See a Shop:
    • If replacing the cabin filter and cleaning the evaporator doesn't resolve the issue.
    • If you suspect a clogged AC drain tube and are uncomfortable accessing it.
    • If the airflow is still very weak after a new filter, indicating a potential issue with the blower motor or other internal components.
    • If the smell persists and you notice any signs of water leaks inside the cabin, which could point to a more serious issue.

Start with the cabin air filter replacement; it's often all that's needed.

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