If your car heater is blowing cold air, you aren’t alone. Most of us will go through a situation like this at some point in our lives.
There are a few possible causes for this situation, but let’s state the obvious: your car’s heater isn’t working. Yes, it sounds silly to say, but now that we’ve identified this as the problem, we can work on how we’re going to fix it.
In this article, we’ll go through how the heater works in a car, some common problems that might cause cold air to blow out, and their solutions.
Hopefully, you’ll find your answers within.
Why Do Cars Have Heaters?
It sounds silly to point out, but cars need heaters to keep their cabins warm. The “cabin” is where you sit, along with any passengers, in your seats.
It’s currently winter. For much of the world, this is synonymous with “pretty cold”. When you leave your home and get in your car, the last thing you want is to find yourself confined in what’s essentially an ice block. Sure, the engine might slowly cause the car to warm up, but you’ll probably have arrived before that happens.
You could catch a cold from merely driving to work.
The heater blows hot air into the cabin to mimic a comfortable environment.
Modern cars have something called “climate control” – ACC. With this option, the temperatures put out by the heater – along with the speeds of the fans, etc. – are continuously adjusted by the car’s ECU, keeping the cabin as pleasant as possible.
Aside from this, we all also now benefit from heated seats, steering wheels, mirrors, windshields, pre-heaters, and so on. The world of driving today is much warmer than it was in the past!
When Was The Car Heater Invented?
The original idea for some kind of heat source in a motor vehicle can be traced back to an American, Margaret A. Wilcox. Ms. Wilcox patented the concept in November 1893. Cars, or automobiles, had just been invented. The American public was only beginning to see the first ones on the roads.
Most of them didn’t have the luxuries of four walls and a roof, also. That wouldn’t be until 1907, when this became more extensively seen on these vehicles.
There still wasn’t any real form of heat in these cars.
About a decade later, some genius came up with the brilliant (please sense the lip-curling levels of sarcasm here!) aftermarket idea of pumping hot exhaust gases back into the cabin. I suppose people were warmer… but they were also overwhelmed by toxic exhaust fumes such as carbon monoxide and died. Don’t ever follow this advice!
It wasn’t until 1929 that the automotive scene first saw something relatively akin to today’s car heater. Ford introduced it as an optional extra – one that would cost you a bit, too. The first car to see this was the Ford Model A. Within a few years, the Model A had a heater that fitted in with the car’s interior aesthetics much more cleanly.
1937 was the year where we saw the first heating and ventilation system that you, the driver, could change and regulate yourself. Nash brought out this system in 1938.
At a similar time, in 1939, the world saw the first (primitive) air conditioning unit.
All of this paved the way for the first ACC (Automatic Climate Control) system on the Chrysler Imperial models. They first brought this out in 1953, before Nash somewhat stole Chrysler’s thunder by introducing its groundbreaking “Weather Eye” system.
These systems led to the modern HVAC systems you find in cars.
When Did The Rest Of The World Catch Up?
The US utterly owned the car heater market. In fact, in the UK and the rest of Europe, it wouldn’t be until the mid-1960s that consumers began to demand car heaters. This demand seems to correspond with the “Big Freeze” – Europe’s winter from 1962 to 1963, which saw snow drifts of up to 20 feet.
Someone even drove a car across the River Thames in London in 1963 for crying out loud. It was cold.
Until this time, all people had were woolly hats and crude aftermarket systems for heating. When Ford showed off its heating system at the London Motor Show in 1964, the entire country was amazed. It wasn’t long before all automotive manufacturers began to follow in Ford’s footsteps.
Eventually, heating systems around the world caught up with the American ones that had paved the way. Come on, world, get it together.
How Do Car Heaters Work?
As mentioned in one of the previous sections of this article, most modern car heaters use heat from the engine’s coolant. This heat is transferred through the heater and blown into the cabin using a fan.
Heaters in electric cars work slightly differently.
First, we’ll consider the average heater on an internal combustion engine (ICE) car.
How Do Heaters Work On Cars With Internal Combustion Engines?
You’ll probably have noticed that it takes time for the inside of your car to warm up. You’ve probably particularly seen this on colder mornings.
There is a reason for this.
Your engine needs to warm up properly first. Once this happens, the system diverts the coolant through the heater core.
The heater system also contains a fan, powered electrically. The fan creates a pressure differential and sucks the hot air from the heater core into the cabin.
How Do Heaters Work On Electric Cars?
When it comes to electric cars, we aren’t quite at the same point of efficiency yet.
It’s well documented that the batteries which power electric cars are substantially less efficient in winter, for a start.
Most electric cars use standard resistance heaters. These are, technically, 100% efficient – that is, the device converts all the electricity to heat. However, they use a lot of charge and can be quite detrimental to an electric car’s performance and range. We’ll explore that a bit further towards the end of this article.
The batteries produce heat. Some cars use a heat pump; the car can recycle some of this heat and pump it into the cabin. This works a bit like reverse air conditioning.
In a Nissan Leaf (a small EV), the heat pump runs off a 1kW compressor and can be used to both warm and cool the batteries. When cooling the batteries, the car can send the excess heat directly to the cabin heater. Many electric cars use a process similar to this.
With newer electric cars, you can set the cabin to warm up before you even start driving. It would be best if you did this with the car plugged into your home, as it draws quite a lot of electrical current. In theory, this heat should last you for most of your journey, especially as many EVs don’t have an extensive range yet.
The heaters found in EVs can be dangerous on long journeys in winter. For example, if you come across stationary traffic and are stuck for many hours, you’ll have to decide between heat and having enough battery power to drive home.
That’s not ideal.
Whether you’re driving an electric car or a traditionally-powered one, always take blankets, warm clothes, and potentially some matches and candles. Anything you might need to keep warm.
What Should I Check When My Car Heater Is Blowing Cold Air?
Before condemning your car heater for blowing cold air, you should check that the problem isn’t caused by something small.
The following situations spring to mind.
- Have you only just switched the car on? If so, the engine might not have got up to temperature yet. The engine won’t send any hot coolant to the heater core until it’s warmed up enough. Otherwise, the coolant going to the heater core will be cold. This would destroy the point of “heating” the car. Check the engine temperature gauge on the dashboard and wait for it to get up to operating temperature.
- Is the air conditioning on? Should this be the case, the air coming out of the vents will be colder than usual. If you’ve still got the heater temperature up high, it won’t necessarily be freezing cold air but might be less than what you’d expect. The air conditioning’s primary function is to remove hot air, and thus you get this result. Switch off the AC and see if it makes a difference.
- Have you got the temperature dial up to maximum and the fan on full power?
If all these basic things are fine – and it is worth checking them, just in case – then there may be something wrong with your car’s heating system.
What Causes A Car Heater To Blow Cold Air?
In this section, we’ll look at what leads a car heater to be blowing cold air into the cabin.
If you have an electric car, the problem is almost certainly something to do with either the heat pump or resistance heater, depending on what the manufacturer’s fitted it with. Since whoever is fixing it might be working with complex electrical circuits, I recommend taking this to a qualified EV mechanic to work on.
All of the following problems involve traditional internal combustion engine-powered cars.
The following items appear in order of what’s easiest to check and fix.
- Coolant levels and leaks.
- Broken or breaking heater controls.
- A thermostat that isn’t working correctly.
- Some kind of heater core problem.
Coolant Levels and Leaks
Coolant is usually made up of 50% antifreeze and 50% water, but can vary depending on the specific manufacturer, make, and model. It keeps the at a limited temperature, preventing any damage from excess heat.
Lift the hood and check your coolant levels. If they’re low, this could be the cause of your heater blowing cold air into your car.
Low coolant levels cause this because there isn’t enough coolant to travel across to the heater core while also cooling the engine.
Top up the coolant with the correct ratio of antifreeze to water. That may fix the problem.
The radiator, coolant reservoir, hoses, pipes, and channels through the engine are all parts of the coolant system.
The cause of your low coolant levels may be a leak. This leak may come from any of the above components.
To check for a leak, leave your car parked on a level surface for a while and then come back to check underneath it. If you see no puddles, check in and around the engine bay.
If there’s still nothing, run the car, letting it get up to temperature. Come back to it after a good while and do the same checks.
You might notice white smoke coming from the exhaust or other problems with the engine’s power output. In this case, you may have a blown head gasket, causing a loss of coolant. Switch the engine off immediately. Unfortunately, you’ll need a significant repair.
Check out this article on Subaru head gaskets for more information on the subject.
Broken or Breaking Heater Controls
Although it might seem like a simple thing to say, the buttons and dials on your center console can get clogged up over time.
Check that this isn’t the case and by making sure all the buttons work.
It can’t hurt to give them a good cleaning. You might want to use precision brushes or Q-Tips to get down the sides of the buttons and dials to remove dust and dirt.
Be careful not to damage any electrical circuitry.
If this doesn’t do it, you may want to replace some of the stuck pieces.
It’s also worth you checking out the heater control valve, if your car has one; you’ll find this under the hood. Its job is to switch the heat off and on. If it gets damaged, it may be permanently stuck in the “off” position, causing the heater to be blowing cold air into your car.
To fix this, simply replace it.
On older cars, the controls work using mechanical switches and cables. You should check these are all working too.
If you have an OBD II code reader on hand, plug it in and see what results you get. It may tell you that you have a broken thermostat.
Aside from this, another telltale sign of a broken thermostat is when your engine’s temperature gauge never moves from “C”.
When a thermostat stops working, the coolant won’t be directed through the heater core. As a result, the heater core will stay cold. When you turn the fan speed up, it will simply blow this cold air out at you.
Thermostats, on the majority of cars, are a relatively easy fix. You should be able to do it yourself. They’re also pretty cheap – expect to pay out much less than $30 or $40 for many cars. Alternatively, you could pay a mechanic to do the work for you. Doing this would likely cost upwards of $140 due to labor charges.
This video explains thermostats and the entire coolant system in more detail.
Heater Core Issue
Heater core issues are probably the most difficult to fix. However, if you’ve ruled everything else out, this may well be the root problem.
The heater core works in the same way as a radiator: it disperses heat. Once the engine is up to temperature, the thermostat opens to allow the coolant to flow through it. The core is made of either aluminum or brass tubing. As this warms up, the air around it warms up too.
The fan – the one you control when you “turn the fan up or down” – then “sucks” the air around this out and into the cabin.
You’ll find the heater core at the back of the dashboard. If your car has vents in the dashboard – used for blowing hot air onto the windshield – it will likely be somewhere underneath that. You’ll usually find it on the passenger side, behind the glove box.
If you notice any of the following symptoms inside the cabin, it could indicate a heater core problem.
- A hazy fog blowing into your car.
- You may also notice a sweet, almost fruity-smelling odor.
- Water/antifreeze on the floor, usually on the passenger side.
- If your car uses coolant very quickly, but you can’t find a leak anywhere, it may be in the heater core. Your car will be using coolant up very quickly and the engine rapidly overheating.
You can try fixing a heater core by flushing it, or you can just replace it if that doesn’t work.
Common Car Heater Questions
Do I Really Need My Car Heater?
I suppose you don’t need your car heater, but you should keep it maintained and ready, just in case.
As current events in Texas are showing us, cold weather can come unexpectedly and find us unprepared. Keeping your car’s heater working makes sure you can prepare for this eventuality.
Of course, you might live in one of the hottest areas of the world and never see temperatures that even approach “cold”. And, it’s true, for those of you that live in these areas, you might never use the heater in your car, ever.
But one day, you might need it. It’s best to keep it maintained and working just in case, even if it isn’t a legal requirement.
Does Turning The Heater Off Save Fuel? (ICE)
Turning your car’s heater off won’t make any noticeable difference to your fuel economy, despite what you may have heard.
Okay, technically, it does affect it, and positively. However, the difference is so minuscule that it’s not likely to be measurable.
Where does this idea come from?
Well, the heater is powered electrically. The more power you instruct the heater to use (the faster you tell the fan to spin), the greater the electrical load. The alternator generates this electricity. A serpentine belt powers it, often referred to as the fan belt. The crankshaft drives the fan belt.
Every component that runs off the fan belt is technically resisting the crankshaft’s motion, thereby slowing it down. Those components also include the air conditioning, power steering pump, etc. – as well as the alternator.
Since the alternator, as one of these components, applies a drag force to the belt and therefore the crankshaft, it technically reduces its power output.
I say “technically” there with emphasis.
Modern engines are advanced enough and efficient enough that the drag effect is barely noticeable.
Turning off the heating may make a minute difference to your car’s power and fuel efficiency, but only a minute one.
There are stronger arguments out there for your air conditioning causing fuel inefficiency and power reduction. Still, even this is barely noticeable in a modern car.
Overall? Nope, you’re probably much better off just leaving your heating on if you need it.
Does Turning The Heater Off Save Battery Power? (Electric Cars)
The short answer is: ooooh yes. So much.
Serhat Sahakalkan, who works in Stuttgart as the project manager at the Fraunhofer Institute for Manufacturing Engineering and Automation IPA, has this to say:
In the most unfavorable case, you can only drive half the usual distance with the car.
Read the full story here on phys.org.
There’s an industry expert explaining that the heater in an electric car can more than halve your car’s range.
Electric cars then, it seems, are so far made for summer and warm climates.
Over time, the technology will, undoubtedly, improve. But for now, the less you’re using your heater in your electric car, the better.
Should I Get An Aftermarket Heater?
There’s certainly nothing wrong with aftermarket car heaters. They might not look as nice as those built into your car, but they should certainly work.
If you quite simply can’t find the problem with your heater and want to avoid a large expense, then it may be worth investing in an aftermarket heater.
Check out this video to see a few of your options.
If your car heater is blowing cold air into your cabin space, I hope some of the above issues may have solved your conundrum.
To sum up, these issues usually involve coolant because your heating system runs using coolant.
I hope you can use this article to fix your problem and have hot air blowing in no time.
These tools have been tried and tested by our team, they are ideal for fixing your car at home.