my GMC Sierra T1XX (2019-Present) has a bad smell when the AC is on, why?

GMC Sierra T1XX (2019-Present)

Error Codes

1-2 hours

Time

medium

Difficulty

medium

Severity

3 min read

535 words

Problem Statement

Learn how to diagnose and fix bad smells from the AC in GMC Sierra T1XX (2019-Present). Step-by-step guide with symptoms, diagnostic steps, and repair instructions.

Affected Component

HVAC

Estimated Time

1-2 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Disconnect the battery before working on electrical systems.
•Ensure the vehicle is turned off and cool before working on the AC components.

Symptoms

•Unpleasant odor when AC is running
•Musty smell, often resembling mold or mildew
•Reduced airflow from the AC vents
•Increased humidity inside the cabin
•Occasional fogging of windows

Diagnostic Steps

1
Inspect the cabin air filter for dirt or mold accumulation.
2
Check the AC drain for clogs or blockages.
3
Examine the evaporator core for signs of mold or mildew buildup.
4
Look for any signs of leaks or moisture in the AC system components.
5
Use an OBD-II scanner to check for any related fault codes.

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 canister
•Coil cleaner
•Flexible wire or cleaning brush

Parts Required

•Cabin air filter
•Evaporator coil cleaner (if mold is found)

Related Faults

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Solution

1. Preparation

Gather all necessary tools and parts.
Ensure the vehicle is parked on a level surface.
Disconnect the vehicle battery to ensure safety while working on electrical systems.

2. Remove Cabin Air Filter

Open the glove compartment and remove any contents.
Locate the cabin air filter access panel.
Remove the access panel by unclipping or unscrewing it.
Carefully pull out the old cabin air filter.
Inspect the filter for debris and odors.

3. Clean or Replace Cabin Air Filter

If the filter is dirty, clean it with compressed air or replace it with a new filter.
Make sure the new filter is installed correctly, following the airflow direction indicated on the filter.

4. Inspect and Clean Evaporator Core

If you suspect mold on the evaporator, access the evaporator core through the dashboard.
Use a specialized coil cleaner and follow the instructions on the product to spray onto the evaporator core.
Allow the cleaner to sit as per the manufacturer's instructions, then rinse with water if applicable.

5. Clear AC Drain

Locate the AC drain tube under the vehicle.
Use compressed air or a flexible wire to clear any blockages in the drain tube.
Ensure that water can flow freely through the drain.

6. Reassemble Components

Reinstall the cabin air filter access panel.
Reconnect the vehicle battery.