car heater blows cold air – possible reasons and what you should do

Our cars are not only a means of transport, but also offer an appropriate level of comfort during journeys. It is hard to deny that vehicles have become an indispensable part of our daily lives.

When winter rolls in and temperatures drop, you love to ride in the cozy cabin of your car. You turn on the heating, but wonder ? Why is my heater blowing cold air into my car?

Instead of just scratching your head for hours and then spending hundreds of dollars on a mechanic later, you may want to try some fixes that we offer.

We also introduce you to the possible causes of this malfunction, so that you can take precautions later on.

Possible reasons why your heater is blowing cold air

Low coolant level

Coolant is 50% antifreeze and 50% water. This fluid is primarily responsible for supporting the heating system. When you turn up your heater, this coolant facilitates the flow of heat in your cabin. However, you should keep in mind that it’s okay if your heater only blows cold air for the first minute and then blows hot air, because your engine usually takes some time to heat up in the winter.

However, if this lasts longer, it is definitely an indication of a low coolant level, which could be due to a fuel leak or radiator/hose issues.

Fix : Top up the coolant level to the required mark using the manual of your vehicle. A coolant change is usually covered as part of the routine maintenance cycle and can cost around $150-160. However, if the problem is due to a leak, get ready to challenge $600-800. However, we recommend that you try to find the leak yourself and see if you can fix it yourself.

Thermostat impairment

The thermostat acts as a valve to regulate the amount of coolant flowing to the radiator. As soon as you start your engine, the thermostat will turn on when it reaches a threshold temperature. After that, the thermostat will allow the coolant to flow downward.

Your thermostat can be stuck either open or closed. If it is closed, the coolant motor will overheat faster and destroy itself over time. Of course, since no coolant can flow into the heater core, only cold air comes in.

On the contrary, if the thermostat is stuck open, the coolant flow is continuous, resulting in a cold heater core.

  • Park your vehicle and make sure it is stationary
  • Make sure that the engine is completely cooled down when you start it
  • Unscrew the thermostat housing present at the end of the upper housing for the heater core.
  • Replace the defective thermostat with a new one and then screw it tightly to the system.

Defective radiator

Technician holding dirty air filter for car

A heater core with dust and lint can also be the reason your heater is blowing cold air. Since the passage through the core is quite narrow, there is a high chance that dirt and grime will build up on the surface over time.

The fins inside the core can also become easily clogged.

Fix: Manual cleaning of the core can solve the problem in most cases. For the inside of the heater core, flushing the core can be very helpful. This can cost you anywhere from a hundred to a few hundred dollars on average.

Jammed mixing door

A blocked mixing damper can prevent hot air from entering the cabin. Apart from this, your heater buttons can also get stuck, resulting in poor air circulation. Prolonged use often leads to such problems.

Fix: Replace the gear depending on the model of your vehicle.

Air bubbles in the cooling system

The elevated position of the heater in the system can often cause air bubbles to enter the coolant. Heat is then not transferred properly, resulting in a cold heater core.

  • Disengage the heating system to the maximum.
  • Remove the coolant tank cap and fill the coolant to the brim.
  • Fire up the engine once and leave the fuel cap still open.
  • After a few minutes, you will notice that the thermostat is on.
  • Now close the lid and test your heating system.

How a car heater works

Car heating systems are divided into three types: water-cooled engines, air-cooled engines and electric. However, since the problem we are focusing on is more pronounced in water-cooled engines, let’s find out how these engines work.

Water-cooled engines operate on the basic principles of heat. As the temperature of your engine rises, it generates heat, which then helps transfer hot air into the cabin. However, constant exposure to heat can cause your engine to overheat.

To combat this problem, these engines have a component called a Coolant which absorbs the heat to prevent overheating. Once the coolant is heated to a few hundred degrees, the heat flows through the radiator into the thermostat, which lowers the temperature.

To remove the hot air, a small heater core is also placed along with a built-in fan to blow the air out.

In summary, the heat generated by your engine flows through a coolant, which then heats the radiator and then transfers heat in the cabin through a fan.

What if the air is warm but not hot enough?

Low heat may be due to loose plugins somewhere in your system. In addition, your thermostat could also be stuck, causing the hot coolant in your heater core to be low. This results in a warm air sound instead of a hot bump.

If your thermostat is stuck in a partially open position, the heater core may not be receiving enough coolant. In addition, as your car ages, the radiator can also pick up small particles of dirt and debris that cause it to block, impairing / slowing its function.

But don’t worry, because regular maintenance and a regular coolant change can easily fix this problem.

Regular maintenance helps a lot

Most problems related to your engine and cooling system can be fixed if you change your fluid regularly. This also improves the quality of your transmission. Since a transmission swap can cost anywhere from $2000 something? $6000, it only makes sense to spend some of that amount at regular intervals instead.

  • OEM oil change, quarterly
  • Tire rotations, twice a year
  • Checking the engine’s faulty transmission, quarterly

Now that you know the real reason for the cold air coming out of your car heater, you can keep yourself from wilting in a harsh winter. Most of these issues can be fixed without help, while some require the expertise of a professional.

But if you’re a person for whom comfort is a priority, these upgrades and fixes will be worth your penny.

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