Why is my car AC blowing hot air

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Why is my car AC blowing hot air? It can be due to low refrigerant level, bad compressor, condenser, cooling fan motor, cooling fan blades, or bad cooling fan switch. It’s better to consult an expert mechanic for complete diagnosis and repair.

This article is a brief guide where we discuss each factor in detail. Starting with how car AC systems work and ending with what can cause car AC to blow warm air.

How does the car AC system work?

The car AC system combines the working of seven components to deliver clean cold air. These components include a compressor, condenser, expansion valve, evaporator, cooling fans, blower fan, and cabin air filter. 

  • The AC system has a fluid called refrigerant that circulates within these components. This refrigerant takes heat from incoming air so it feels cold inside the car cabin.
  • AC system working starts from the compressor that compresses and pressurizes the refrigerant. This pressure helps the refrigerant to move through all other components. 
  • After the compressor, refrigerants enter condensers that remove heat from refrigerants using cooling fans. 
  • Condensers pass refrigerant to expansion valves that further reduce the refrigerant temperature.
  • Evaportant takes extremely low-temperature refrigerant from the expansion valve. 
  • There is a blower fan that blows air over the evaporator fins. Air loses its heat due to the extremely low temperature of evaporator fins.
  • Air then passes through the cabin air filter and enters the car cabin.

If any of the above-mentioned components fails to work properly then the AC system might overheats the car and even blo warn air in car.

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why is my car ac blowing hot air

Why is my car AC blowing hot air

The car air conditioning (AC) system is responsible for delivering cold air into the car cabin. If the AC system malfunctions, it can blow hot air. The malfunction can be due to seven reasons and we will discuss all of them here. 

1. AC System has a low level of refrigerant

First and the most common reason why your car is blowing hot air is that it has a low level of refrigerant. With a low quantity of refrigerant, the AC system will not be able to cool the incoming air. Due to this, you will feel hot air coming out of your car AC. 

You can check the refrigerant level in your car by checking its pressure at low and high-pressure ports. 

  • At the low-pressure port, the pressure should be about 25 psi minimum and 45 psi maximum.
  • At the high-pressure port, the pressure should be about 250 psi minimum and 400 psi maximum.

2. AC compressor or compressor clutch has turned bad

The AC compressor has multiple parts working together to compress the refrigerant. If any of the compressor components has worn out and is not working properly. Then the compressor will not be able to develop the required refrigerant pressure.

Without the required pressure, the refrigerant will not flow properly. With low refrigerant flow, the AC system will blow hot air as it cannot lower air temperature properly.

Another common problem with compressors is the bad compressor clutch. There is a clutch to connect the compressor with the car engine through serpentine belt. If the clutch turns bad then it cannot transfer complete power to the compressor.

With low power transfer, the compressor will develop low pressure and thus AC will blow hot air into the car cabin.

3. Dust accumulated or clogged tubes of AC condenser

AC condenser is responsible for cooling the refrigerant. If the outer fins or tubes’ outer surface of the condenser are accumulated with dust and debris then it will not be able to cool the refrigerant.

Similarly, if there is any clogging in AC condenser tubes, then refrigerant flow will be compromised. This reduced cooling effect of the condenser and refrigerant temperature does not lower the required value.

Due to this, your car AC will blow hot air into the car cabin. You can easily clean the outer surface of the condenser with pressurized water. To remove clogging, you need to flush the condenser properly.

4. AC condenser cooling fan blades are accumulated with dust or broken

Depending on the car’s make and model, there can be one or a pair of cooling fans. They are always installed at the front of the car under the hood. 

In most modern cars, first, there is a condenser, then there is a radiator, and then the cooling fans.

If the car cooling fans are accumulated with dust, then they cannot draw air over condenser tubes properly. This reduces AC system performance. A similar thing will happen with broken blades.

Cooling fan blades can be washed with pressurized water. Broken bald means you need to replace the fan.

5. AC condenser cooling fan motor is dead

If the cooling fan is not rotating at all, then the cooling fan motor is dead. The cooling fan is powered using a 12-V DC motor. 

These motors are exposed to harsh conditions while driving. The dust, debris, and water can damage the cooling fan motor.

It’s not difficult to replace the cooling fan motor. You can do this in a few simple steps.

6. The AC condenser cooling fan switch has turned bad

The same cooling fan is used to cool condensers and radiators. So there is a switch installed on the radiator that automatically switches on and off the cooling fan when needed.

This switch senses the heat and can switch on and off the cooling fan as needed. If this switch has turned bad then your cooling fan will not turn on when at a very high temperature.

No fan running means no cooling of refrigerant in the condenser. No cooling of refrigerant means your car AC will blow hot air into the car cabin.

7. AC system wiring has a short circuit

There is a high chance that all components of your car’s AC system are working properly. The only bad thing is the wiring or fuse that connects the cooling fan motor, switch, and controls present inside the car cabin.

The only solution for this is to replace the bad wires or fuse as soon as possible.

Last Words

Why is my AC blowing hot air in my car ? Low refrigerant level in the AC system is one of the 7 reasons why your car blows hot air. It can also be a bad compressor, condenser, or cooling fan.

If you still have any questions, do ask them in the comment section and we will respond accordingly.

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