How to Get Your Heavy-Duty Truck’s AC Ready for Warmer Spring Temperatures

As winter fades and temperatures rise, heavy-duty truck drivers and fleet operators need to prepare their vehicles for the shift in seasons. One of the most overlooked aspects of seasonal maintenance is the air conditioning (AC) system. A properly functioning AC isn’t just about comfort—it also prevents driver fatigue, reduces humidity inside the cab, and ensures clear visibility by defogging windows.

Neglecting your AC system before warm weather sets in can lead to unexpected breakdowns, costly repairs, and uncomfortable drives when you need cool air the most. To keep your system running efficiently, follow this step-by-step guide to getting your heavy-duty truck’s AC ready for spring.

Step 1: Inspect the AC System for Visible Damage

After months of cold weather and little to no AC use, start by performing a visual inspection. Open the hood and check the AC compressor, refrigerant lines, condenser, and electrical connections for signs of wear, corrosion, or leaks.

Look for cracked hoses, loose belts, and visible refrigerant leaks. Refrigerant leaks often appear as an oily residue around fittings or along the hoses. If you notice green, yellow, or clear oily stains, your system may have lost refrigerant and need professional service.

The condenser, located at the front of the truck near the radiator, should be free of dirt and debris. A blocked condenser can cause the system to overheat and reduce cooling efficiency. So a quick inspection to remove any leaves, dust, or road grime with a soft brush or compressed air will extend the life of your AC.

Step 2: Test the AC’s Performance

Before hitting the road in warm weather, turn on the AC and let it run for a few minutes to assess its functioning. Set the blower to the highest setting and check if cool air is coming from the vents. If the airflow is weak or warm, there may be an issue with the blower motor, refrigerant level, or clogged expansion valve.

Pay attention to any strange noises such as clicking, grinding, or hissing. These sounds can indicate a failing compressor, loose belt, or refrigerant leak. A musty or mildew smell coming from the vents suggests mold or bacteria buildup in the evaporator core or cabin air filter.

Step 3: Check and Replace the Cabin Air Filter

The cabin air filter plays a crucial role in keeping dust, pollen, and debris out of the truck’s ventilation system. A dirty or clogged filter can restrict airflow, reduce cooling efficiency, and create unpleasant odors inside the cab. Most heavy-duty trucks have easily accessible cabin air filters located behind the glove compartment or under the dashboard. Remove the filter and inspect it for dirt buildup. If it’s clogged with dust, pollen, or debris, replace it with a new one. For trucks operating in high-pollen areas like North Carolina, South Carolina, or Georgia, it’s best to replace the cabin air filter at least twice a year to maintain optimal airflow and air quality.

Step 4: Check the Refrigerant Levels

Refrigerant is essential for cooling the air in your truck’s AC system. Over time, refrigerant levels can drop due to small leaks, worn-out seals, or natural evaporation. Low refrigerant levels cause the AC to blow warm air and make the compressor work harder, potentially leading to premature failure.

To check refrigerant levels, connect a pressure gauge to the AC system’s low-pressure port. The ideal pressure range depends on your truck’s make and model, but for a typical R-134a system, the pressure should be between 25-45 PSI when the system is running.

If the levels are low, you may need a refrigerant recharge. However, topping off refrigerant without fixing leaks is a temporary solution. If your system frequently loses refrigerant, have it inspected by a professional to locate and seal any leaks.

Step 5: Inspect the AC Compressor and Clutch

The AC compressor is responsible for circulating refrigerant and pressurizing the system. If the compressor isn’t engaging, the AC won’t cool properly. A failing compressor may also make loud clicking or grinding noises, indicating internal wear. When you address compressor issues early you can prevent costly repairs or full system failure.

Start the truck and turn on the AC. Watch the compressor clutch—it should engage and start spinning when the AC is activated. If it doesn’t engage, the issue could be:

• Low refrigerant levels, prevent the clutch from activating.
• A faulty AC relay or fuse.
• A damaged compressor clutch requires replacement.

Step 6: Clean the Evaporator and Condenser Coils

The evaporator coil absorbs heat from the truck’s cabin and allows the refrigerant to cool the air. Over time, dust, mold, and debris can clog the evaporator, reducing cooling performance.

To clean the evaporator:

• Use a compressed air blower or soft brush to remove dust buildup.
• If there is mold or mildew, apply a non-corrosive AC coil cleaner.
• Ensure the evaporator drain line is clear to prevent water buildup and mold growth.

The condenser coil, located at the front of the truck, releases heat from the refrigerant. If it’s covered in dirt or debris, cooling efficiency decreases. You should spray the condenser with a hose or use compressed air to remove the buildup.

Step 7: Test the AC Blower Motor and Vents

Weak airflow from the vents can indicate an issue with the blower motor or ventilation system. If the blower motor is failing, it may produce grinding or squealing noises when running. Check the ventilation mode settings to ensure air is correctly redirected between the dashboard vents, defrost vents, and floor vents. If air isn’t flowing properly, a stuck blend door actuator or blocked duct may be the cause. If the airflow is still weak after replacing the cabin air filter and cleaning the evaporator, the blower motor may need lubrication or replacement.

Step 8: Preventative Maintenance for the Summer

Once your truck’s AC system is up and running for spring, keeping it in peak condition throughout the summer requires ongoing maintenance. A well-maintained AC system not only keeps drivers comfortable but also reduces strain on the engine and electrical system, leading to better fuel efficiency and lower operating costs. You should:

• Run the AC at least once in a while, even on cooler days, to keep the compressor lubricated.
• Check for refrigerant leaks periodically to prevent costly failures.
• Keep the condenser free of debris for maximum cooling efficiency.
• Replace the cabin air filter every 6 months, especially in high-dust or pollen-heavy areas.

Stay Cool and Comfortable on the Road

Spring is the perfect time to prepare your heavy-duty truck’s AC system for rising temperatures. By performing a thorough inspection, checking refrigerant levels, replacing filters, and ensuring all components function properly, you can avoid costly repairs and downtime during peak summer months.

Whether you're driving through the humid climates of North Carolina, South Carolina, or Georgia, a properly maintained AC system will keep you comfortable, alert, and ready for long hauls. Southeast Fleet Services takes a proactive approach now will save money, reduce stress, and keep your truck running efficiently all season long. For more information about winter maintenance, read our article on frozen brakes.