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Car's A/C, Air Conditioning Repair, Refrigerant, Compressor

Why Does My Car’s A/C Blow Hot Air?

Car's A/C, Air Conditioning Repair, Refrigerant, CompressorNow that summer is in full swing, the temperatures are rising and it’s getting really hot outside. I love cranking up my car’s A/C to stay cool during my daily commute. But this summer, my car’s A/C did nothing but blow hot air out of the vents! What should be done in situations like this? Having routine maintenance on your car’s A/C system can prevent costly air conditioning repair, and most importantly, keep that cold air flowing all summer long. Read on to learn how your car’s A/C works, when to recharge the refrigerant, and just how vital the compressor is to a well working air conditioning system.

How Your Car’s A/C System Works

A car’s air conditioning system is a fairly complex array of components that need to work in unison to be effective. The Compressor is basically a pump attached to your engine’s crankshaft. It compresses a Refrigerant (low-pressure gas) into a high-pressure gas – a process that creates heat. That heated, high-pressure gas is then cooled down in the Condenser, which turns it into a liquid.

During this process, moisture may be created through condensation and needs to be removed via the Receiver-Dryer. Then it travels through the  Thermal Expansion Valve or the Orifice Tube which allows the high-pressure liquid to expand. Now the refrigerant is a cold, low-pressure liquid when it enters the Evaporator (usually in the car’s cabin) and absorbs the hot air inside it. A fan blows the cold air inside, while the heat is taken outside. This process turns that cold, low-pressure liquid into a warm, low-pressure gas again and the process begins all over.


Back in the day, Freon was used in most air conditioning systems. However, it was determined that Freon harmed the ozone, so a slightly safer alternative (R-134a or HFC-134a) was developed and put in use in all cars after 1996. If your car is low on refrigerant, then that may be why the A/C is blowing hot air. It is a closed system, so low refrigerant means there is a leak somewhere that will need to be found and repaired asap. Leaking refrigerant is not safe (according to the EPA), and can cause very costly repairs down the road, if not addressed.

A/C Compressor

The compressor is what starts the whole process of your air conditioning. If it wears out or becomes damaged, the air will still flow through the system, but it will not be cold. Unfortunately, replacing a faulty compressor is fairly expensive. Expect to pay $500 – $800 (or more, depending on your specific car).

A good way to keep your compressor in good working order is to run it for 10-15 minutes every 30 days or so, all year long. A compressor that sits idle too long can become compromised and may not work when the weather finally warms up.


The condenser looks like a small radiator, and it functions much like one too. The hot liquid refrigerant moving through the many tubes is cooled down. If any of the tubes inside the condenser are blocked, then the fluid cannot move through the system or cool down. If the fluid stays hot, then your car will be blowing hot, instead of cold, air into the interior. 

Another possible reason would be a cracked or broken tube inside the condenser. If this happens, refrigerant will leak. If there is not enough refrigerant in the A/C system, the air may blow hot, and severely low refrigerant could cause irreversible damage to the system.


The receiver-dryer is a small reservoir that contains desiccants, small grains that attract water. It is important to make sure no water gets into the evaporator since the temperature of the refrigerant can go below the freezing temperature of water. While the refrigerant will not freeze, any frozen water crystals in the system can cause damage.

Thermal Expansion Valve (TXV) or Orifice Tube

The TXV and the orifice tube perform the same function, but your system will only have one of them. The TXV has moving parts that can wear out and require replacement. The orifice tube has no moving parts, but it can get clogged with debris which needs to be addressed to keep your A/C running properly.


The evaporator is usually located in the cabin of the car and also looks like a radiator. Its job is to absorb the heat from the air inside the car and take it outside. A fan blows on the cold coils generated by the low-pressure liquid, the coils absorb the heat from the air as it moves through the evaporator, and you are left with a cool interior. If there is an issue with the system before it reaches the evaporator, then you will get warm or hot air blowing into the car because the refrigerant is not the super cold low-pressure liquid it needs to be to generate cold air.

Recharging Auto A/C

If the refrigerant in your car’s A/C is low, it can be topped off by a service technician. If it is really low, however, it will need to be drained, cleaned and refilled in a process called Recharging. Low refrigerant is a sign that there are bigger issues at play, and the technician should find the source of the leak and you should have it repaired.

Air Conditioning Repair

A&R Complete Auto Care has been providing Clarksville, TN with dependable and trustworthy Auto Repair since 2009. We provide excellent routine maintenance services and use the most current diagnostic equipment available to quickly diagnose, and professionally repair, all of your auto air conditioning issues.

Schedule a Service for Your Car’s A/C

Give us a call at (931) 552-0606 or visit us online to make your A/C Service appointment today!

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1111 Fort Campbell Blvd, Clarksville, TN 37042 Phone: (931)552-0606