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2021 CT4 AC Smells & Low Airflow - Cabin & Engine Air Filters?

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Brittany E. · rep 0 · May 22, 4:02 AM · 1 replies · solved · Question

Vehicle: 2021 Cadillac CT4 Premium Luxury

Hello everyone,

I own a 2021 Cadillac CT4 Premium Luxury with the 2.0L turbo engine, and it's got about 30,000 miles on it. Lately, I've noticed that the AC isn't blowing as strong as it used to, and there's a bit of a musty, stale smell coming from the vents when I first turn it on. It's not terrible, but it's definitely noticeable.

I'm thinking it might be time to replace both the cabin air filter and the engine air filter. Are these relatively easy to access and replace on the CT4? What's the recommended service interval for these filters, and could a dirty cabin filter really cause that smell?

Thanks for the help!

✓ Accepted solution

ClearTheCode Admin

ClearTheCode Team · rep 0 · May 22, 4:02 AM

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Hi Emily,

Your observations of reduced AC airflow and a musty smell are classic symptoms of a dirty cabin air filter, and it's a great idea to check your engine air filter as well. At 30,000 miles, both are likely due for inspection or replacement.

Causes of Your Symptoms:

  1. Clogged Cabin Air Filter: This filter traps dust, pollen, leaves, and other debris from entering your car's HVAC system. When it gets clogged, it restricts airflow, leading to reduced fan output. Moisture trapped in the filter can also lead to mold and mildew growth, causing that musty smell.
  2. Dirty Engine Air Filter: While less directly related to cabin smell, a dirty engine air filter restricts airflow to the engine, potentially impacting fuel efficiency and engine performance. It's a critical maintenance item.

Recommended Service Intervals (General Guidelines):

  • Cabin Air Filter: Typically every 15,000-20,000 miles or once a year, more frequently if you drive in dusty environments or have allergies.
  • Engine Air Filter: Usually every 30,000-45,000 miles, or as recommended in your owner's manual. Again, dusty conditions warrant more frequent checks.

DIY Feasibility on 2021 CT4:

  • Cabin Air Filter: This is generally a very easy DIY job on most Cadillacs, including the CT4. It's typically located behind the glove compartment. You'll usually need to unclip or remove a few screws to drop the glove box, then slide out the old filter and insert the new one. There are many online tutorials specific to the CT4 that can guide you.
  • Engine Air Filter: Also a straightforward DIY. It's usually located in a housing on top of or to the side of the engine. You'll typically unclip a few fasteners or remove a few screws to open the airbox, remove the old filter, and drop in the new one.

When to See a Shop:

  • If replacing the cabin air filter doesn't eliminate the musty smell, you might have mold or mildew deeper in the HVAC system (e.g., on the evaporator coil), which might require a professional AC system cleaning or a specialized evaporator foam cleaner.
  • If, after replacing both filters, you still experience significant airflow issues or engine performance problems, there might be other underlying issues that require professional diagnosis.

Replacing these filters is a cost-effective way to improve your driving comfort and maintain engine health.

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