Car A/C is Blowing Hot Air: How to Diagnose the Causes

blowing hot air

Did you experience your car’s air conditioning is blowing hot air instead of cooling the cabin? Know how to diagnose its causes and find solutions to this problem, only here.

Your car’s air conditioner is supposed to provide you comfortable cool air inside the cabin, but if your car’s A/C is blowing hot air, there must be something wrong with the system. The most common comfortable temperature people want inside their car goes anywhere between 20 to 22C (68 to 72F). While others want a slight variation on this range, too high a temperature is really uncomfortable!

It is really frustrating to experience that your air conditioner is giving you headaches instead of comfort cooling during the hottest time of the day. So, before you panic and decide to bring your car to the nearest service center, you may want to know first the causes of this inconvenience. Your service center might less likely take advantage of you regarding an unreasonable cost of charges when you know why your car’s A/C is blowing hot air.

What you will need

    • Pressurized air (from an air compressor)
    • Condenser replacement kit (optional)
    • Soft-bristle brush (or an old toothbrush)
    • Leak Stop aerosol
    • Condenser-fin straightener

To find out what causing your A/C to blow hot air

Here are some of the most common troubleshooting techniques auto technicians do when diagnosing an A/C system of a car when it blows warm air rather than a cold one. It’s better to have some knowledge about your car’s essential parts that could save you a substantial amount of cash if you can do the minor repairs. But it is still the best to consult the professionals when major problems arise.

  • Checking the condenser

The condenser of your car’s A/C system is similar in appearance from your radiator (with coils or small tubes arranged the same as the radiator), it is only smaller. Most newer cars have the condenser placed at the front of the car so it is easily accessible for visual inspection. The condenser is utilized to cool the compressed coolant (the refrigerant in this case) into ambient temperature coming from the system’s compressor.

Air is blown to the condenser via a fan that is run by a separate mechanism. If the cooling fan is in good running condition but there is no air that blows through the condenser, the refrigerant will pass through the expansion valve with a higher temperature than it usually does. And rather than cooling the coolant to a comfortable level, it will only be cooled to atmospheric condition or might be higher, causing your A/C to blow hot air.

Here’s what might happen to the condenser as you can check it out by visually inspecting it and what you can do correct the problem.

  • The condenser might be clogged by some debris, such as leaves, plastic bags, hardened dirt, sticks, rocks and other objects. 

The best thing to do here is to rub the coils and the tubes with a soft-bristle brush to remove the dirt. You can also take away the objects that block the airways. After brushing, you may subject the coils to air cleaning via high-pressure air, but be careful not to deform the fins as they are thin and can be easily bent.

  • The condenser might be punctured that enables the refrigerant to leak

If this might be the case, you can check for leaks by adding a UV dye on your A/C system to easily spot the leak. Or you can add a Leak Stop aerosol in a can (such as the Enviro-Safe Refrigerants ProSeal - view detail on to permanently seal the leak (if leaks are minute). This is done by adding this compound to your A/C system. Working instructions come with the product so you don’t have difficulty adding this sealer to your A/C system.

But if the puncture is so immense and repairing it is out of the question, replacement is inevitable. However, before you seek the help of the professionals, you can replace this unit yourself. You can order a car A/C Condenser online and make a DIY repair to save you some precious dollars from expensive fees from labor if you seek the services of a qualified mechanic.

This condenser is commonly placed in front of the car and has only a few mounting bolts on its frame. There are only 2 refrigerant lines that are easy to remove and instructions can be easily followed in replacing the unit.

  • Checking the refrigerant

A low level of refrigerant is the most common cause of an A/C system that blows hot air. Inadequate coolant level may happen due to leak on the system resulting from loose connections of hoses, worn out hoses, leak on fittings or the escape of the refrigerant over time. The low state of coolant could be corrected by recharging the system and adding ProSeal (for minor leaks) to the system to make sure it is sealed permanently and charging is continuous.

You can also replace the leaking hoses with new ones. These hoses are easily available from your local automotive store.

  • Checking the condenser fan

The A/C condenser will be able to cool the refrigerant if only the air around it is cool enough and its fan is the one which does this job. The fan moves the air rapidly around the condenser and its fins, a malfunctioning or a broken one will impede the flow of cool air around the system which will result in hot air being blown by the air conditioner.

Additionally, the condenser fan cools an important element of your air conditioning system, it is only proper that you pay so much attention to its normal operation when you notice that your A/C blows hot air instead of cool air.

The cooling fan worn-out over time that causes it to stop working. Without a working condenser fan, your car may overheat. When you suspect that the AC condenser fan has a problem, better to have your car checked by a qualified technician.

Some important advice

If you want a more affordable replacement for your punctured condenser, try the best-selling Diversitech EL3232-2 E-Lite Plastic Condensing Unit Pad from Amazon. This low price brand is easy to install and does not need specialized tools for installation, you can also save more when you use this product.

If the fins of the condenser are accidentally bent, you may want to use a fin straightener instead of using other objects (such as a comb or a stick) that may totally deform them. Try the one recommended by the professionals, such as the ATD Tools 304 Condenser Fin Straightener, also available from Amazon.

The Enviro-Safe Refrigerants ProSeal is totally safe for your condenser and goes well with an A/C system that uses R-134A as a refrigerant. This aerosol does not crystallize and repair minor leaks in the fittings, condenser, evaporator, and even in the metal lines.


Did you enjoy our tutorial for today? There are really more to learn when your car’s air conditioning is blowing hot air, which is unusual for such a device. This sign is not to be ignored the moment it should happen to you because this may develop into a more elaborate and costly problem once it becomes full blown.

Knowing how to diagnose a problem like this in your car will certainly put you on the edge of better car maintenance which will be more beneficial to you in the long run. Please send us your comments and share this article if you liked it.

About the author

Carolina - Care My Cars

Car, from a long time ago is the main transport vehicle for people which help to move faster and protect users from the unstable of weather such as sunlight, heat, or rainy. So that, the demand of car and the search for the best and a suitable car in the market are higher than ever and you also are one of the people who is looking for the answers from the market. Welcome to and I hope that my articles can help you to solve the problems that you are in with the most effective way. If you think my website give values, you can donate me by the ways. Donate: - Bitcoin (BTC): 1Eoz8vhfAjD4cCrq2jec3V38mmaHehedXU - Etherium (ETH): 0xd10809ae634117bf6c52Af884a8bc8B84D436e3b - BicoinCash (BCH): qqp4yjqx2g57exes0stsnkgk5e9uyu5clvrjj4ew44 Thank for all

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