Why is My Car Heater Blowing Cold Air and How to Fix It?

Is your car heater not blowing hot air when idling or driving? If yes, then you may be wondering, “Why is my car heater blowing cold air, and how to fix it quickly?” Isn’t it? Don’t worry; you aren’t the first person who is facing the problem of cold air blowing out of vents when heat is on in the car.

On the freezing mornings when driving feels impossible, car heaters come to your aid as nothing less than an angel. They keep our car and you warm and ensure that you are comfortable. As much as you want your air conditioning to work on a scorching day, car heaters are much required when the wind blowing out there is deathly.

But what if your car heater betrays you on a cold morning when there are miles ahead of you? People keep asking, “why is my car heater not working properly” or “why is my car heater blowing cold air intermittently?”. It is a common problem that troubles every car owner, and if you are one of them presently, this guide is perfect for you.

car heater blowing cold air
(Disclosure: This post contains affiliate links and images. I earn advertising/referral fees if you make a purchase by clicking them. There is no extra cost to you. See our full disclosure here. )

Yes, your car heater may sometimes blow cold air or not heat properly as it should. There are several reasons why it happens, and there are ways in which you can deal with it. This comprehensive guide discusses how car heaters work and how to fix a car heater blowing cold air or car heater not working properly.

You will learn several ways to fix a car heater that blows cold air and some of the most common questions about why is my car heater not blowing hot air and how to fix it. So, read on and learn how to make your car heat hotter.

How Does a Car Heater Work?

Before you get around your heater with your toolbox, you must know how does a heater work in a car and what are the car heating system components. A car is a machine, and every part works in combination with several other parts. Therefore, your car heater does not work in isolation.

So, first of all, let’s check out what are the essential components of an automotive heating system. A car heating system includes:

  • Heater core
  • Heater hoses
  • Blower motor
  • HVAC control panel
  • Heater control valve

Then there are cooling system components in your car, such as the radiator, thermostat, coolant, and water pump. These systems work in unison to make your car work in the best possible manner without overheating it or cooling it excessively.

Now, come to the question of “how a car heater works?”. Your engine heats up as you drive, and it needs to be passed out. The exhaust system comes into play here and takes care of most of the heat. At the same time, the rest of the heat remains in the engine cast and is transferred to the coolant.

As it reaches a higher level, the thermostat opens, and the coolant flows in and passes the heat around the engine to the radiator and to the heater core, which exchanges the heat and sends the heat into the car cabin.

how does a car heater work

This heater can be controlled and adjusted to the desired level. The heater core is situated under the dashboard or on the passenger side wall under HVAC. The blower motor is the component that blows the air through the heater core and warms the car and passenger side.

The coolant flows through the heater core, and the control valve controls the flow of this coolant. This valve is found in a heater hose and controls the output of the heater.

As you see, you need your car’s cooling system to be in excellent condition to heat your vehicle. Your coolant and water must be a proper mix and at the right temperature, i.e., 32 degrees Fahrenheit. The thermostat must be working correctly to open and close at the right time.

In addition to these functions, the water pump should be pumping correctly so that the coolant passes through the radiator and heater core without any problem.

Since now you know what are the basic components of an automotive heating system and how does a car heater work, let’s move forward to learn what causes your car heater to blow cold air and how to fix a car heater blowing cold air when idling or driving.

Must check: Why is My Car Air Conditioner Blowing Hot Air and How to Fix It?

Why is My Car Heater Blowing Cold Air and How to Fix It?

The process of troubleshooting car heater blowing cold air problems isn’t straightforward and quick because, unfortunately, a fault in any of these car heating system components (thermostat, coolant, heater core, heater control valve, blend door actuator, heater fan, or blower motor resistor, etc.) or any unexpected circumstances (water leaks, or air in the cooling system, etc.) can make you wonder “why is my car heater not getting hot enough.”

There are several reasons why your car heater is not blowing hot air or why your car heater blows cold air when idle and warm air when moving. And that’s why we have come up with this detailed guide where we are going to help you learn some of the most common reasons why your car heater blows cold air and how to fix it as quickly as possible.

So, without further ado, let’s have a look at the reasons and solutions to figure out what does it mean if your car heater is blowing out cold air and how to fix a car heater not blowing hot air when driving or idling. Here we go:

Faulty Thermostat

The bad or failing thermostat in car is one of the most common reasons why your car heater is not blowing hot air. A thermostat is the one that reads the temperature and opens up to allow the coolant to flow off through the radiator. So, if it stops working or gets stuck, the car temperature will not work correctly.

If your thermostat gets stuck in a closed position, the coolant will not flow to the radiator and cool the engine, which will excessively heat your car. On the other hand, if the thermostat gets stuck in an open position, it means that the coolant will keep flowing to the radiator and heater core and won’t warm your car at all.

How to tell if a thermostat is bad in a car? You can confirm a faulty thermostat easily. First of all, you have a thermostat needle on your dashboard that switches from “C” to “H” as the temperature reaches a warming level. If you see the needle stuck on “C,” there is a problem.

And if you are going to look at the radiator, let the car cool down first. Now open the radiator cap, which is located in the front as you open the hood. It is a small metal cap.

Start the engine and look into it, and if you see the coolant flowing even when the car has only started up, it means the thermostat is stuck open, and the coolant is flowing continuously. That’s why your car heater is not blowing hot air.

So, if your car thermostat has gone bad, you need to replace it as quickly as possible if you want to get rid of the problem where your car is blowing out cold air instead of heat.

Contaminated Coolant or Low Coolant Level

Wondering what causes the car heater to blow cold air? Check your coolant level. Yes, it is one of the most essential car heating system components which plays a crucial role in keeping your car hot. Contaminated coolant and low coolant levels in the vehicle are also among the most common reasons why your car heater blowing cold air and not getting hot enough.

The coolant is the component that flows through the engine cast, radiator, and heater core and blows hot air into the cabin. It is made up of 50% antifreeze and 50% water. If the level of the coolant goes down, it hampers the heating.

There are reasons why coolant’s level goes down. For example, if any hose is leaking or a problem with the radiator or any other heating components, there is not enough coolant in your system.

To fix it, first, check if the coolant is leaking. If it is, take it to a mechanic so he can check the component and fix it. If you can do it yourself, it is well and good as a coolant replacement, or filling costs an average of $160 to $200 apart from the professional’s labor cost.

If you have identified that there is a leak, take your car to the mechanic as soon as possible without letting it cause any further damage to the vehicle.

Bad or Clogged Heater Core

Another car heating system component that is involved in heating your car is the heater core. If this small but crucial part gets clogged, it may cause the car heater not working properly issue. The heater core is small, and it also has external fins which allow the hot air to fill the vehicle cabin. It is most common that debris, dust, and other particles clog it.

If the coolant level is acceptable, you must lookout for the following signs which indicate a problem with the heater core:

  • A sweet and fruity odor
  • Fog inside the car
  • An overheating engine
  • Car using coolant quickly than normal

When the heater core is clogged, the coolant can’t flow properly, so the cold heater core keeps blowing cool air all the time. To fix this clogged heater core, you need to flush it or clean it manually. You can use a cloth and remove any debris or dust that you can see on the external parts. If it doesn’t resolve the issue, take it to the professional.

Most often, flushing does it for you, and you can get your heater core fixed by paying approx $80 to $90. However, if the part needs to be changed, it will cost you up to $250 without a professional’s cost.

Air in the Cooling System

Can air in cooling system cause car heater blowing cold air issue? This problem does not indicate any other sign than complaints from the users that the car heater is not working properly. But it is something which definitely hampers the heating system. So, what happens if there is air in the coolant system?

If the air contaminates your coolant, it doesn’t heat the car. Big bubbles in the coolant do not let the heat get adequately transferred and cause the heater not blowing hot air in car. This is a problem that can be handled easily.

Are you wondering how to get air out of cooling system? If yes, follow the steps mentioned below, and fix the air bubbles in the cooling system:

  • First of all, set your car’s heating to the maximum.
  • Remove the cap from the coolant tank.
  • Fill the tank with coolant to the brim.
  • Now start the engine while the lid is still open and let it run.
  • If the coolant level goes down, fill it again.
  • It will allow the air bubbles to leave the tank while it is open.
  • When the engine is hot and the coolant level is not falling, close the tank.

This process does not cost money if you can do so on your own. If you take it to the mechanic for the same, it won’t cost much as there is no replacement or requires any specialized skills. However, if the problem is not the air bubbles, the mechanic will determine the problem.

Broken Heater Controls

Every component in your car has a life which also greatly depends on how you use them. If you are someone who takes excellent care of your car, the parts work for years without causing any issues. But, if you have kids who love to play with controls while you drive, well, you know what happens.

If you are still wondering, “why is my car heater not blowing hot air?” even after checking the coolant levels, leaks, thermostat, and heater core, then you should definitely check the heater controls.

Sometimes, the problem may not be with any internal component but the simple heating control, which goes bad after years of usage. They may get stuck, get damaged, or clogged and thus not work properly and blow hot air.

The only way to fix the broken heater controls is to replace them. The cost of replacing them depends greatly on the car you use.

Jammed or Broken Blend Door Actuator

Have you ever wondered how the same vent in your car blows both cool and hot air from time to time? Ever thought about a blend door actuator? No. If your car heater is not blowing hot air, it’s time that you should learn about the blend door actuator and what it does.

It plays many major roles. It is a small plastic gear set which moves to allow the desired temperatures of air to blow out. It allows air to pass based on the circulation modes such as the floor, mid vent, or defrost. It switches the temperatures from cold to heat. It allows the heat to blow from the system to the cabin.

If this door gets stuck or breaks, the hot air will not pass, and the problem of the car heater blowing cold air will persist. This may be caused by a broken or damaged switch, a problem with a vacuum line, or some other reasons.

The only solution to fix this issue is to get it replaced. As it is an internal component, lots of handiwork is required on your mechanic’s part. The parts cost somewhere between $450 to $500 without labor cost. Depending upon where you live, the labor cost can come somewhere around $500.

Faulty Heater Fan

So your car heater blows cold air then hot, and you have checked the coolant, and there is no problem. You checked the heater core, air bubbles, and every possible component, and there is no problem. But most often than not, you overlook the component which is right in front of your eyes, and that is the heater fan.

You fire up the engine, switch the controls, and the hot air starts to flow in the cabin in a few minutes. The heater core, coolant, thermostat, etc., work together, and the heater fan blows the heat. When this fan goes bad, now air comes out of the vents, and you freeze.

A heater fan can get damaged due to a short circuit or damage to any internal components, or any other reason. The only solution is to get it checked and replaced. It costs around $90 to $300, including parts and labor.

Failing or Bad Blower Motor Resistor

It is the car heating system component that controls the fan speed. The knob that you use to change the speed is connected to the blower motor resistor, which changes the speed. If you frequently change the settings, it may cause the blower motor resistor to go off.

So, if your car heater not working properly and you are filled with amazement to figure out” why is my car heater blowing cold air instead of hot air” you must check a few things first such as:

  • If the vents are not blowing hot air at certain settings, or
  • If the fan is working on one speed only, or
  • No air is coming off the vents at all.

If you find any of these signs, it confirms that your blower motor resistor is the reason why heater in car not blowing hot air.

Once again, it is an internal component, and fixing it on your own is a bit complex. So, it would be best if you had a mechanic. If it needs replacement, it cost around $100 to $160 for parts alone.

Water Leaks

If your car heater blows cold air intermittently, you need to crouch down and see if there is a water puddle under your car. As it is said earlier, your coolant is a mixture of 50% water and 50% antifreeze, and if any of this is leaking, it is a problem.

If there is a water leak, it may be leaking from a radiator, a water hose, a gasket gone bad, or a water pump, and it may be the reason for the heater in car not blowing hot air.

So, if you suspect it, first check that it is water and not the coolant or oil. Put a paper under the car and let it absorb the liquid. Smell it. A coolant smells sweet, while water has no odor. Leaking water is not a big deal, but it can result in a bigger one if you don’t give it proper attention.

If you have identified why water leaking from the radiator or a gasket needs to be changed, you can do it yourself if you know how to do it. Else, taking the car to the mechanic is the best option. The cost of repairing a water leak depends on the reason why it is leaking.

Must see: 13 Best Portable AC for Cars and Trucks and Our Best Picks for You is…

Car Heater Blowing Cold Air Intermittently [FAQs]:

If you are called for work early in a december morning, you are freezing, but the heater in car is not blowing hot air, several questions (such as how does a car heater system work, why is my car heater not blowing hot air when idling or driving, and how to fix a car heater blowing cold air) come to your mind.

While all the possible reasons have been discussed above, it doesn’t stop you from wondering; why car blows cold air when idle and warm air when moving, how much does it cost to replace a heater core, or what are the symptoms of a bad thermostat in your car? Right?

Well, don’t worry! Here are some of these most frequently asked questions answered for your ease to fix a car blowing out cold air instead of heat. Let’s check them out:

How Long Should You Let Your Car Warm Up in the Winter?

Well, it is your car, and it was out in the garage all night. Warming up your car isn’t essential unless it is a 30-year old vehicle that hiccups as you drive. For less than 30-year old or newer cars, you only need to give it 30 seconds or so.

Don’t just start it and get it out on the road. In the winter season, you need to be patient so that you don’t freeze when you step inside it. Drive it out of the garage and turn on the defroster and the engine. Let the engine run for at least 30 seconds.

If your car is out in the open and it is covered in snow, remove the snow and let it run for almost a minute or so. Then step in and start it. Drive slow for the first 5 to15 minutes so that the engine has time to warm up properly.

How Much Does It Cost to Replace a Heater Core in a Car?

If your car heater blows cold air, then hot, and the problem is with the heater core, you wonder how much does it cost to replace a bad heater core. Isn’t it?

The heater core is situated under the dashboard or the passenger side firewall. If it gets clogged or some other problem arises, it needs to be flushed or replaced.

While the average heater core flush service will cost you $80 to $90, the replacement cost may come around $564 to $927. This cost depends upon various factors such as the parts that need to be replaced, the labor cost where you live, and the time required to fix it.

How Do I Know If My Car Needs a Thermostat?

You must look for symptoms of a bad thermostat in the car if your car heater blows cold air. You need to check if: If your car engine is overheating in no time, or If the temperatures are changing dramatically, or The coolant is leaking around the thermostat, or Car heater not blowing hot air.

If any of these symptoms are visible, take your car to the mechanic and get it checked. Of course, you can also check it at home, but if you are not very handy with car parts, professional help is recommended.

How to Fix a Car Heater Blowing Cold Air – Author’s View

This problem doesn’t start all of a sudden, and you face it if you neglect your car and maintenance. And when the winters arrive, and you turn on the heat, you feel disappointed and start thinking, “Why is my car heater not blowing hot air, and how to fix it if the car heater not working blowing cold air?”.

This comprehensive guide has explained the 9 possible reasons why your car heater is not blowing hot air and how to fix it. If the cold air blowing out of vents when heat is on in car, go through the above-explained methods and check all the essential components of the car heating system individually.

Sometimes, you can fix the car blowing out cold air instead of heat problems all by yourself, while sometimes, calling a professional for the job is the best option.

The most common problems that affect the car heating system are thermostat problems when your reading does not stir from “C,” and the cold air in the car seems to kill you. Then there are broken heater controls in plain sight, but you don’t suspect them to betray you.

One more usual problem is the coolant leak or low coolant level in the car, which car owners most often experience. Look for the puddle under your vehicle and confirm that it is not water.

The water leak is also a considerable problem. Be it any kind of leak from your car, and it needs to be fixed. The best and quick solution to deal with a car heater blowing cold air instead of hot air is to take it to a professional. The cost of fixing different problems varies depending upon the “to-be-replaced” parts and labor cost. That’s all!

We hope now you know everything about the car heating system components, how they work to keep you warm inside your car, and how to fix a car heater that blows cold air then hot. If you found this guide, “why is my car heater blowing cold air and how to fix it?” helpful for you, feel free to share it with your friends. Have an excellent winter driving!

You may also be interested in checking out:

About Jace

I am an automotive enthusiast who loves to be around cars and pickup trucks. Applying innovative car care products and installing different latest car accessories are my hobbies. Also, I love sharing my adventurous experience with car lovers.

Leave a Comment