Air Conditioning Troubleshooting

July, 2025

When your fleet is driving longer and hauling more during the intense summer heat, a working A/C system becomes essential. When your semi-truck’s air conditioning starts blowing hot air or stops working, downtime isn’t an option.

We’ve created a helpful guide to help you troubleshoot common air conditioning issues, avoid breakdowns, and stay ahead of costly repairs.

1. A/C Blowing Warm Air? Start Here

If your A/C is on but you’re not getting cold air, you could be experiencing a number of these issues:

• Low Refrigerant (Freon): This is usually the most common culprit. Your refrigerant may experience a slow leak or loss naturally over time and usage. If your system cycles on and off frequently, a new refrigerant may be needed. Shop top-selling Weitron refrigerants and get your A/C blasting cold air again.
• A/C Compressor Issue: The main part of the A/C system is the A/C compressor. If the compressor clutch isn’t engaging, you may be experiencing a faulty compressor, or the electrical signal may be disrupted. Learn how to replace your compressor with our how-to guide here.
• Clogged Cabin Air Filters: Don’t overlook these! A dirty or clogged cabin air filter limits airflow and puts more stress on your A/C system.

2. A/C Smells Bad or Has Weak Airflow

If the air has a musty smell or is barely coming through your vents:

• Replace Cabin Air Filters: An old or clogged filter is a common source of musty smells and poor airflow.
• Check for Mold or Mildew: Moisture buildup in the evaporator can cause mold. Try running the fan on high with the A/C off before shutting the truck down to help dry the system.
• Inspect the Vents: Make sure nothing is blocking your vents from blowing air. Paper, trash, or small items stuck in the vent can cause poor airflow.

3. A/C Only Works While Driving

If your air works when you’re moving but weakens at idle:

• Cooling Fan Failure: When there’s not enough airflow when you’re not driving, the issue might be the condenser fan.
• Low Refrigerant: Having low refrigerant weakens cooling power, especially when idle.
• Clogged Condenser: Dirt or bugs can weaken airflow. Check for buildup on the front of your condenser and clean or replace if needed.

4. Preventive Tips

• Replace your cabin air filter at least once every 25,000 miles.
• Keep an eye on your A/C compressor, belts, and hoses.
• Don’t ignore small warning signs like a slow decrease in cooling power. This usually means it’s time to service your A/C system.
• Run your A/C system periodically, even in the winter, to keep seals lubricated. This will help to prevent early cracks or leaks.

Stay Ahead of the Heat

If your A/C system isn’t performing like it used to, it’s worth checking it out before small problems turn into bigger issues. Routine A/C maintenance keeps your fleet running smoothly through the hottest months of the year.

For reliable A/C parts and expert advice, visit FleetPride.com. Our wide range of products and Heavy Duty Experts™ can help you select the correct A/C parts for your truck. Why compromise comfort and reliability? Visit FleetPride.com today!

*The foregoing is provided for informational purposes only. Please consult your local FleetPride Heavy Duty Experts to verify the suitability of a part for the intended application.