my Volvo XC90 makes a weird musty smell when I turn on the AC, why?

Volvo XC90 Second Generation (2015-2024)

Error Codes

2-4 hours

Time

medium

Difficulty

medium

Severity

3 min read

477 words

Problem Statement

Learn how to diagnose and fix the musty smell from the AC in your Volvo XC90. Step-by-step guide with symptoms, diagnostic steps, and repair instructions.

Affected Component

HVAC

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical systems.
•Ensure the vehicle is turned off and cooled down before starting repairs.

Symptoms

•Musty odor when the AC is turned on
•Possible increased humidity inside the vehicle
•Moisture on the interior surfaces
•Reduced airflow from the AC vents
•Presence of mold or mildew in the cabin

Diagnostic Steps

1
Inspect the cabin air filter for debris or mold.
2
Check the AC drain tube for blockages or clogs.
3
Examine the evaporator core for signs of mold or mildew.
4
Look for water leaks inside the cabin that may contribute to moisture.
5
Test the function of the blower motor for adequate airflow.

Solution

💡 Expert Tip

For complex repairs like this, consider taking photos at each step. This helps if you need to reverse a step or consult with a mechanic. Also, keep all removed parts organized - you may need to reference them during reassembly.

Verification

After completing the repair, verify that the issue has been resolved:

✓Test the affected component to ensure it functions correctly
✓Check for any error codes or warning lights
✓Monitor the vehicle for a few days to ensure the issue does not recur

Prevention Tips

To prevent this issue from occurring again:

•Follow the manufacturer's recommended maintenance schedule
•Address warning signs early before they develop into major issues
•Use quality parts and fluids recommended for your vehicle
•Keep detailed records of all repairs and maintenance

Tools & Equipment Required

•Screwdriver set
•Compressed air source or flexible wire
•Evaporator cleaner spray
•Safety gloves

Parts Required

•Cabin air filter
•Evaporator cleaner (if needed)

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Solution

1. Preparation

Gather necessary tools and parts.
Disconnect the battery to ensure safety while working on electrical components.

2. Cabin Air Filter Replacement

Locate the cabin air filter compartment, typically behind the glove box.
Remove the glove box by unscrewing or unclipping it.
Remove the old cabin air filter and inspect for mold or debris.
Install a new cabin air filter (ensure it meets OEM specifications).
Reassemble the glove box.

3. Clear AC Drain Tube

Locate the AC drain tube, usually found under the vehicle on the passenger side.
Using compressed air or a thin flexible wire, clear any blockages in the drain tube.
Ensure water drains freely when the AC is running.

4. Clean Evaporator Core

Access the evaporator core by removing the HVAC housing (may require disassembling dashboard components).
Use a specialized evaporator cleaner spray to clean the core, following the manufacturer’s instructions.
Allow the cleaner to sit for the recommended time, then rinse if required.
Reassemble the HVAC housing securely.

5. Dry Out the System

Run the AC on high for 10-15 minutes with the windows open to help eliminate residual moisture.
Monitor for any odors during and after the drying process.