Is Your Car’s AC Not Cooling Properly? Potential Causes Explained

Key Highlights:

• A blocked cabin air filter, a dirty condenser, or a weak blower motor can restrict airflow into the cabin.
• The most common cause of inefficient AC cooling is low refrigerant levels.
• To keep the system working effectively, ensure you turn on the AC at least twice a week, even in winter.

Components of a Car AC System

Before learning about faults, it is wise to know the main components of an automotive air conditioning system. Here is a brief overview:

• Compressor: Circulates the refrigerant throughout the system, compressing it into a high-pressure, high-temperature gas.
• Condenser: Positioned at the front of the car, it cools the high-pressure gas and turns it into liquid (as a result of heat transfer).
• Receiver or Dryer: Removes moisture and filters impurities from the refrigerant while also storing excess refrigerant.
• Expansion Valve: Controls the flow of refrigerant into the evaporator.
• Evaporator: Located inside the dashboard, it absorbs heat from the air and cools it before blowing it into the cabin.
• Blower Fan: Pushes cool air through the vents.
• Refrigerant: The special gas or fluid that absorbs and releases heat, thereby allowing cooling.

Common Problems in Car AC Systems

A car’s air conditioning system is a mix of mechanical and electronic parts that work together to provide optimal cooling and control. Over time, issues such as refrigerant leaks, dirty filters, worn compressors and electrical faults can reduce its effectiveness. Let us discuss some common car AC problems:

Low Refrigerant Levels

The most common cause of weak cooling is a low refrigerant level. Over time, tiny leaks in the pipes or seals can let the refrigerant escape. If the level is not correct, the system will not be able to absorb enough heat.

Fix: A technician will inspect for leaks, repair them, and recharge the system with the correct amount of refrigerant. Refrigerant refilling is best left to professionals who have the correct equipment and take necessary safety precautions.

Faulty Compressor

The compressor operates continuously whenever the AC is on, drawing power from the engine via a dedicated pulley and clutch mechanism. With age, the engine belt or ‘serpentine belt’ might come loose, thus reducing the efficiency of various vital components, including the compressor.. If the compressor fails, the AC refrigerant cannot circulate.

Fix: In most cases, replacement is required. Regular use of AC, even in winter for short periods, keeps the compressor lubricated and extends its life.

Blocked Condenser

The condenser sits in front of the radiator and is exposed to dirt, leaves and road debris. Blockages restrict airflow, causing the refrigerant to cool down improperly.

Fix: Cleaning the condenser fins and ensuring no external damage helps restore operational efficiency. If the condenser is leaking, replacement is necessary.

Electrical Issues

Modern AC systems rely on sensors, switches and the ECU. A blown fuse, a bad relay, or faulty wiring can prevent the compressor or fan from operating.

Fix: Diagnosing electrical faults often requires professional equipment. Replacing damaged wires or relays usually restores function.

Clogged Cabin Air Filter

The cabin filter traps dust and pollen before air enters the cabin. Over time, it gets dirty and restricts airflow, leading to weak cooling and foul odours.

Fix: Replacing the cabin air filter regularly is a simple and inexpensive way to maintain good AC performance.

Faulty Blower Motor

If the blower fan is not working correctly, cool air will not be pushed through the vents. This can be due to worn bearings, a bad resistor or broken wiring.

Fix: Depending on the fault, either the motor or the resistor may need to be replaced.

Evaporator Problems

The evaporator can get clogged with dust or mould. In some cases, it may develop leaks. This reduces cooling and can cause water to drip inside the cabin.

Fix: Cleaning or replacing the evaporator typically resolves the issue, although it usually requires dismantling the dashboard.

Strange Noises and Smells

Whistling, rattling or grinding sounds from the AC may signal a failing compressor or fan. Foul odours often come from bacterial growth inside the evaporator.

Fix: Noises must be checked immediately to avoid bigger damage. For smells, disinfecting the system with special sprays helps. Regular use of AC reduces moisture buildup, preventing mould.

What’s Involved in Car AC Repair?

Timely servicing ensures the system remains efficient and prevents expensive replacements. A standard car AC service or repair job usually involves:

• Checking refrigerant levels and topping up if required
• Inspecting hoses, belts and seals for wear
• Cleaning the condenser and evaporator
• Replacing the cabin filter if needed
• Running leak detection tests
• Testing system pressure and cooling performance

Maintenance Tips for Optimal Car AC Performance

Modern car AC systems are designed to run with minimal maintenance, unlike those in cars from the 2000s or earlier. While major repairs should be done only by those who have the right know-how, simple preventive measures are worth considering.

Run the AC Regularly

Even in winter, switch on the AC for a few minutes every week. This keeps the compressor lubricated and prevents seals from drying out.

Clean the Condenser

Check the condenser for dirt or debris whenever you wash your car. Gentle cleaning helps maintain proper airflow.

Replace Cabin Air Filter

Change the cabin filter every 12 to 18 months, or earlier in dusty conditions. This ensures smoother and cleaner airflow into the cabin.

Service the System

Get the AC inspected by a professional at least once every two years. They will inspect every critical component, including the compressor clutch, refrigerant levels, and hose leaks.

Prevent Moisture Build-up

After using AC for a long drive, run the blower without AC for a few minutes before shutting down. This helps dry the evaporator and reduce mould growth.

Signs Your Car's AC Needs Repair

Understanding the common issues with air-conditioning systems enables owners to take timely action and ensure a pleasant driving experience throughout the car’s ownership. Obvious warning signs should not be ignored, as early repair prevents complete failures and high repair bills. Here are some common signs of a faulty car AC unit:

• Cooling takes too long, or lower temperatures cannot be attained
• Airflow from vents feels weak
• Unusual noises when the AC is on
• Water droplets inside the cabin
• Frequent fogging of windows
• Burning smell or musty odour

Most of these problems can be avoided or solved with regular maintenance such as cleaning, filter changes and professional servicing.

FAQs

1. Why does water leak inside the car when the AC is ON?
A clogged drain pipe can cause condensation water to overflow inside the cabin. Cleaning the drain usually fixes the issue.

2. Why is the AC compressor not engaging?
It may be due to low refrigerant pressure, a blown fuse or a damaged clutch coil.

3. Why does the AC stop working in traffic but cools while driving?
It may be due to a faulty condenser fan or poor airflow when the vehicle is stationary.

4. Why does my AC make the engine feel strained?
The compressor, when running, puts additional load on the engine. If the AC causes the engine to stall or strain excessively, the compressor may be faulty.

5. How often should I service my car's AC?
It is good practice to service the AC once a year. This includes checking refrigerant levels, filters, belts and the compressor.