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My Car A/C is Blowing Hot Air

Ac car troubleshooting

My car ac is blowing hot air, supposed to be car air conditioning blows cold air instead of hot air. What seems to be a problem, let's take a look first at some parts of the car air conditioning system to have a little background. 


The air conditioning system has what it calls the “Refrigerant”, a substance that is considered as the lifeblood of the car air conditioning. The refrigerant is the one that absorbed the heat from the car passenger compartment with the help of what is called the evaporator, of course when the heat is absorbed in one area that area will become cold, just like what happens to the car passenger compartment in which becomes cooler.

Once the refrigerant absorbed heat, it will become hot and it changes its form from a liquid into gas, this gas will then passes into a part called the compressor, this part served as the heart of the system. The gas will then be compressed and passes into the condenser to cools down and return to its liquid form so that it can absorb heat again. This is a repeated cycle that your car air conditioning system does.

The refrigerant in the car cooler does not disperse outside but repeatedly changes from liquid form to vapor and then back to the liquid form. This cycle is called a refrigeration cycle and the air-cooling system performs it continuously. Generally, the temperature of the gas rises when it is compressed and it becomes liquid when it is cooled. It returns to vapor when it is decompressed. In the refrigeration cycle, the refrigerant (Freon gas) is compressed by the compressor. Then the compressed vapor, at a high temperature and high pressure, is cooled in the condenser and becomes a liquid.


The liquid refrigerant is evaporated by reducing its pressure with the squeezing operation of the expansion valve. This evaporation soaks up heat from the surrounding air. The figure illustrates the basic steps making up the refrigeration cycle, together with the flowing direction, pressure levels, and conditions of the refrigerant.

Now, let’s go back to the problem. When the air conditioning blows hot air this only means that the refrigerant does not absorb the heat coming from the passenger compartment and it only happens when there is no refrigerant that passes into the evaporator. With that said the most likely reason why there is no refrigerant in the system, that it has a leak somewhere on the system or the condenser is clogged.

Of the two reasons stated above, a clogged condenser is only a contributing factor the main problem is a refrigerant leak.

Possible cause of car A/C blowing hot air


(1) A refrigerant leak.
(2) Clogged condenser
AC car troubleshooting

How to fix a car air conditioning blowing hot air


The first thing to do when having this kind of problem is to check the condenser for any debris, dirt, or bug that is build up outside the condenser. The condenser is usually found mounted in front of the radiator. Try cleaning the condenser with a soft brush and spray with pressurized water to remove the debris that blocks the air to pass through the condenser to cool the refrigerant. This will improve the performance of your car air conditioning system.

Car AC Not Blowing Air From Vents
When the car ac is not blowing air from vents in the car it is a sign of a faulty blower fan or air duct blockage. A faulty blower fan can make the car ac stopped working suddenly.
Learn more: Car AC not Blowing Air from Vents

After cleaning if there is still a problem, then the possibility is there is a leak somewhere in the system. Bring the car to a reputable auto shop that specializes in car air conditioning system. Ask the mechanic to check for leak then repair if necessary. Take note that a clogged condenser is just a contributing factor to why the car air conditioning blows hot air and not blowing cold air. The main problem is a refrigerant leak in which you need to replenish the system with enough amount of refrigerant after the leak is repaired.

All new cars use a different type of refrigerant these days compared to old cars, cars now use R134a refrigerants which is environment-friendly. Old cars use R12 refrigerants which are already banned because of their hazardous effect on the environment. If your car still uses R12 refrigerant it would be better to ask your mechanic to convert your car air conditioning system to the one that is cheaper and environment-friendly refrigerants like the R134a.



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