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How to Fix AC in Car Blowing Hot Air

If you’ve ever experienced your car’s AC blowing hot air instead of cold, you know how frustrating and uncomfortable it can be. Especially during the summer months, when you need your AC the most, having a malfunctioning system can ruin your driving experience. Not to mention, it can also affect your car’s performance and fuel efficiency.

That’s why it’s important to address the problem as soon as possible and ensure that your AC system is functioning properly. But before you can fix the issue, you need to understand what causes it in the first place.

Understanding the Causes of Hot Air

There are many possible reasons why your car’s AC may blow hot air instead of cold. Some of them are minor and easy to fix, while others may require more complex repairs or professional assistance. However, some of the most common ones are:

  • Low refrigerant levels: This can happen due to leaks or lack of use. You may need to recharge the refrigerant or repair the leaks.
  • Electrical system issues: This can happen due to blown fuses, frayed wires or faulty switches. You may need to check the wiring and replace the faulty components.
  • Faulty compressor: This is the part that pumps the refrigerant around the system. If it fails, the AC will not work at all. You may need to replace the compressor.

To address these causes, you need to follow specific troubleshooting steps that will help you identify and fix the problem.

Troubleshooting Low Refrigerant Levels

One of the most common causes of a car AC blowing hot air is low refrigerant levels. Refrigerant is the substance that absorbs heat from the air and cools it down before it reaches your cabin. If there is not enough refrigerant in the system, the AC will not be able to cool the air effectively.

To check the refrigerant levels in your car’s AC system, you will need a pressure gauge and a thermometer. Here are the steps to follow:

  • Locate the low-pressure port on your AC system. It is usually marked with a blue cap and located near the firewall.
  • Attach the pressure gauge to the port and turn on your car and AC.
  • Read the pressure reading on the gauge and compare it with the recommended range for your car model. You can find this information in your owner’s manual or online.
  • If the pressure is too low, you will need to recharge the refrigerant. You can buy a refrigerant kit from an auto parts store or online and follow the instructions carefully.
  • If the pressure is too high, you may have a blockage or a leak in the system. You will need to find and repair the source of the problem or seek professional help.

When recharging or repairing your AC system, make sure to wear protective gloves and goggles and avoid any contact with refrigerant as it can cause skin irritation or eye damage.

Diagnosing Electrical System Issues

Another common cause of a car AC blowing hot air is an electrical system issue. The electrical system controls various components of your AC system, such as the compressor clutch, fans, relays, and sensors. If any of these components fail or malfunction, they can affect the performance of your AC system.

To identify electrical system issues, you will need a multimeter and a wiring diagram for your car model. Here are some steps to follow:

  • Locate the fuse box under your dashboard or hood and check for any blown fuses. If you find any, replace them with new ones of the same rating.
  • Locate the wires that connect to your AC components and check for any signs of damage, such as fraying, corrosion, or melting. If you find any, replace them with new ones of the same type and gauge.
  • Locate the switches that control your AC system and test them for continuity using your multimeter. If they do not show continuity when turned on or off, replace them with new ones of the same kind.
  • Locate the sensors that monitor your AC system and test them for resistance using your multimeter. If they do not show resistance within the specified range for your car model, replace them with new ones of the same type.

When working with electrical components, make sure to disconnect your battery first and avoid any contact with live wires as they can cause electric shock or fire.

Addressing a Faulty Compressor

The compressor is one of the most vital parts of your car’s AC system. It is responsible for compressing and circulating the refrigerant throughout the system. If it fails or malfunctions, your AC system will not be able to cool down the air at all.

To diagnose a faulty compressor, you will need to listen for any unusual noises or observe any signs of leakage or damage. Here are some steps to follow:

  • Turn on your car and AC and listen for any loud or squealing noises coming from the compressor. If you hear any, it may indicate that the compressor is worn out or damaged and needs to be replaced.
  • Check the compressor clutch for any signs of wear or damage. The clutch is the part that engages and disengages the compressor when you turn on or off your AC. If it is cracked, broken, or stuck, it may prevent the compressor from working properly and needs to be replaced.
  • Check the compressor belt for any signs of wear or damage. The belt is the part that connects the compressor to the engine and transfers power to it. If it is loose, frayed, or broken, it may affect the performance of the compressor and needs to be replaced or adjusted.
  • Check the compressor for any signs of leakage or damage. The compressor is a sealed unit that contains oil and refrigerant. If it leaks or cracks, it may cause a loss of pressure and cooling capacity in the system and needs to be replaced.

To replace a faulty compressor, you will need to remove the old one and install a new one of the same kind and size. You will also need to flush the system and replace the refrigerant and oil. This is a complex and costly process that requires specialized tools and skills. Therefore, it is advisable to seek professional assistance if you are not confident or experienced in doing it yourself.

Preventive Maintenance for a Functioning AC System

The best way to avoid AC problems is to prevent them from happening in the first place. By performing regular maintenance on your car’s AC system, you can ensure that it stays in good condition and functions properly. Here are some tips on preventive measures:

  • Use your AC regularly, even in winter. This will help keep the system lubricated and prevent seals from drying out and leaking.
  • Keep your system clean, especially the condenser and evaporator. These are the parts that exchange heat with the air and can get clogged with dirt, debris, or bugs. You can use a soft brush or a spray cleaner to remove any buildup and improve airflow.
  • Schedule professional inspections at least once a year or before summer. A certified mechanic or AC technician can check your system for any issues and perform any necessary repairs or adjustments.

Seeking Professional Assistance

While some AC issues can be fixed by yourself with some basic tools and knowledge, others may require professional expertise and specialized tools. If you are not sure what is causing your AC to blow hot air, or if you lack experience in repairing AC systems, it is best to consult a certified mechanic or AC technician for help.

They can diagnose the problem accurately, provide you with an estimate of the cost and time involved, and perform the repair safely and efficiently. They can also advise you on how to maintain your AC system properly and prevent future problems.


Having a car AC that blows hot air instead of cold can be a frustrating and uncomfortable problem, especially during hot weather. However, by understanding the common causes of this issue, such as low refrigerant levels, electrical system issues, and a faulty compressor, you can troubleshoot them effectively and fix them promptly.

You can also prevent AC problems by performing regular maintenance on your system, such as using it regularly, keeping it clean, and scheduling professional inspections. And if you need any assistance with complex repairs or diagnosis, you can always seek help from a qualified mechanic or AC technician.

By following these tips, you can ensure that your car’s AC system is functioning properly and providing you with a comfortable driving experience.

Editor Staff

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