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Musty Smell from AC in 2022 Terrain - Cabin Air Filter?

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Ryan M. · rep 0 · May 22, 3:45 AM · 1 replies · solved · Question

Vehicle: 2022 GMC Terrain SLE

Hey GMC owners,

I've got a 2022 GMC Terrain SLE, and lately, when I turn on the AC or even just the fan, there's a distinct musty, mildew-like smell coming through the vents. It's not constant, but it's definitely noticeable, especially when I first start the system.

The car only has about 30,000 miles on it, and I haven't changed the cabin air filter yet. Could this be the culprit? I live in a pretty humid area, so I'm wondering if moisture is playing a role.

Is changing the cabin air filter a straightforward DIY job on the Terrain, or should I have the dealership handle it? Any other ideas for getting rid of this smell?

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 3:45 AM

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ClearTheCode admin answer:

A musty or mildew smell from your AC vents is a very common complaint, and your suspicion about the cabin air filter is likely correct. Given your 2022 GMC Terrain's mileage and living in a humid area, it's highly probable that the cabin air filter is saturated with moisture and has become a breeding ground for mold and bacteria.

Here's what's typically happening and how to address it:

  1. Cabin Air Filter: The primary function of the cabin air filter is to trap dust, pollen, and other airborne particles before they enter your vehicle's cabin. Over time, it collects debris and, especially in humid climates, can become damp, leading to mold and mildew growth. This is the most common source of the smell.
  2. Evaporator Core: Another potential source is the evaporator core itself, located behind the dashboard. Moisture naturally condenses on the cold evaporator fins, and if it doesn't drain properly or if the system isn't allowed to dry out, mold can grow there too.

DIY Steps for Cabin Air Filter Replacement:

  • Location: On most GMC Terrain models, the cabin air filter is located behind the glove box. You'll typically need to open the glove box, unclip or remove a few retaining pins/screws, and then lower the glove box to access the filter housing.
  • Replacement: Note the direction of the airflow arrow on the old filter before removing it. Insert the new filter (available at most auto parts stores) with the arrow pointing in the same direction. Reassemble the glove box.
  • Difficulty: This is generally considered a straightforward DIY task that most owners can perform with basic tools (sometimes just a screwdriver) in about 15-30 minutes.

Additional Tips to Eliminate Odor:

  • Evaporator Cleaner: If the smell persists after changing the filter, you might need an AC evaporator cleaner spray. These products are designed to kill mold and bacteria on the evaporator core. Follow product instructions carefully.
  • Run Fan Before Shutting Off: To help dry out the evaporator, try turning off the AC compressor (but leave the fan running) for a few minutes before reaching your destination, especially in humid weather.

When to See a Shop:

  • If the smell persists after changing the filter and using an evaporator cleaner.
  • If you notice water leaking inside the cabin, which could indicate a clogged AC drain line.
  • If you're uncomfortable performing the DIY steps.
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