GMC Sierra T1XX (2019-Present) AC not blowing cold air how to troubleshoot

GMC Sierra T1XX (2019-Present)

Error Codes

2-4 hours

Time

medium

Difficulty

medium

Severity

4 min read

642 words

Problem Statement

Learn how to troubleshoot and fix AC not blowing cold air in GMC Sierra T1XX (2019-present). Step-by-step guide with diagnostic steps and repair instructions.

Affected Component

HVAC

Estimated Time

2-4 hours

⚠️ Safety Warnings

Important safety information - read before proceeding

•Ensure the engine is off and cool before working on the AC system.
•Wear safety goggles and gloves when handling refrigerants and electrical components.

Symptoms

•AC compressor not engaging
•Warm air blowing from vents
•Unusual noises when the AC is activated
•Decreased airflow from the AC vents
•AC system blowing air with a musty or foul odor

Diagnostic Steps

1
Check the AC system settings to ensure the temperature is set to the coldest setting and the AC is turned on.
2
Inspect the AC fuse and relay using the fuse box diagram to ensure they are not blown or malfunctioning.
3
Scan the vehicle’s computer system for any diagnostic trouble codes (DTCs) related to the AC system using an OBD-II scanner.
4
Measure the refrigerant pressure using a manifold gauge set to check for proper levels and potential leaks.
5
Inspect the AC compressor visually for signs of damage or leaks, and check if the clutch is engaging when the AC is turned on.
6
Check the cabin air filter for clogs or restrictions that could affect 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

•OBD-II scanner
•Manifold gauge set
•Basic hand tools
•Fuse puller

Parts Required

•AC fuse/relay (if defective)
•Refrigerant (R-134a or R-1234yf depending on the system)
•AC compressor (if diagnosed as faulty)
•Cabin air filter

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Diagnostic Steps

1
Check the AC system settings to ensure the temperature is set to the coldest setting and the AC is turned on.
2
Inspect the AC fuse and relay using the fuse box diagram to ensure they are not blown or malfunctioning.
3
Scan the vehicle’s computer system for any diagnostic trouble codes (DTCs) related to the AC system using an OBD-II scanner.
4
Measure the refrigerant pressure using a manifold gauge set to check for proper levels and potential leaks.
5
Inspect the AC compressor visually for signs of damage or leaks, and check if the clutch is engaging when the AC is turned on.
6
Check the cabin air filter for clogs or restrictions that could affect airflow.

Solution

1. Preparation

Gather tools and parts: OBD-II scanner, manifold gauge set, basic hand tools, and replacement refrigerant if needed.
Ensure the vehicle is parked on a level surface, and the engine is off.

2. Replace AC Fuse/Relay

Locate the fuse box and identify the AC fuse and relay.
Remove the fuse using a fuse puller or pliers and inspect it for continuity. Replace if blown.
Remove the AC relay and replace it with a new relay of the same specifications.

3. Recharge Refrigerant

Connect the manifold gauge set to the low and high-pressure service ports of the AC system.
Start the vehicle and turn on the AC to the maximum setting.
Check the gauge readings; if the low side is below 30 psi, the system may need recharging.
Follow the refrigerant manufacturer’s instructions to add refrigerant until proper levels are reached (typically 30-40 psi on the low side and 150-250 psi on the high side).

4. Repair or Replace AC Compressor

If the compressor clutch is not engaging, test the electrical connections to the compressor with a multimeter.
If defective, remove the AC compressor by disconnecting the electrical connector and the refrigerant lines (ensure to recover refrigerant properly).
Install the new compressor by reversing the removal steps, ensuring all seals are replaced and tightened to specifications.

5. Check Cabin Air Filter

Locate the cabin air filter housing, typically behind the glove box.
Remove the housing cover and take out the old cabin air filter.
Inspect and replace it with a new filter if it is dirty or clogged.