You jump in your car on a cold, wintery morning and crank the heat up. But after a few minutes, you notice it still isn't blowing hot air! What gives? Learn what's keeping you from enjoying your car's warm air and what you can do about it.
Engine coolant contains a precise mixture of antifreeze and water, which helps keep your engine from overheating or freezing. If your car’s coolant has the right ratio of antifreeze and water, it shouldn't freeze in the winter or get too hot in the summer, ensuring that your car’s cooling system can effectively absorb and dissipate excess heat created in the engine.
When you run your car’s heater in the colder months, some of this excess heat is blown into the cabin to help you stay warm and defrost your windshields! Over time, contamination in your cooling system can make your coolant more susceptible to freezing, which may result in your engine overheating and your heater not working!
The heater core looks (and works) similar to your car’s radiator — it's made up of a series of narrow tubes and fins. However, while the radiator dissipates heat to the surrounding air, heat from the heater core is blown into the passenger compartment by a blower fan.
The heater core’s maze-like network of tubes is susceptible to clogging and leaks, reducing the coolant level or flow through your engine’s cooling system. Faulty heater cores and low or contaminated coolant levels often come hand in hand, and both issues may lead to your engine overheating and your heater not blowing hot air.
Other signs of a faulty heater core include a sweet-smelling scent in your car, windows that become particularly fogged-up, and puddles under the dashboard or on the passenger-side floorboard.
Your car’s thermostat is a valve that opens and shuts to regulate the coolant flow to the engine and radiator. Although it’s a pretty simple device, a functioning thermostat is vital to keeping your engine running at optimum temperature.
A damaged thermostat may become stuck in the open or closed position. When stuck open, the thermostat may allow too much coolant to flow, preventing your car from reaching its optimum operating temperature, thereby causing a decrease in performance. On the other hand, a thermostat that’s stuck in the closed position won’t allow coolant to circulate, interrupting the system that cools your engine and heats your cabin. Yikes!
When you crank up the heat in your cabin, the heater core captures heat from the coolant and transfers it into the cabin in the form of warm air. The blower fan is responsible for ventilating that warm air from the heater core through your car’s vents! However, when the blower fan is not working correctly, you may notice little to no airflow coming from the vents.
Various issues may cause your blower fan to malfunction, including a blown fuse or damage to the blower fan’s internal components. Regardless, if you can barely hear or feel a breeze when your car heater is running, issues with the blower fan may be to blame!
It’s hard to enjoy the ride when your teeth are chattering! Plus, many of the same issues that prevent your car’s heater from blowing hot air can also lead to engine overheating and decreases in performance!
Get a professional opinion on what’s causing your car heater to malfunction and which services and repairs can help fix it at your nearest Firestone Complete Auto Care. With thousands of locations across the country, we’ll get you back en route to your holiday getaway in no time!
It's no fun getting into your car on a frosty winter's morning only to find the car heater not blowing hot air. It's almost as unpleasant to have a car heater that's not giving out enough heat.
If you’re wondering why is my car heater not working, you’re almost certainly wondering how easy it will be to fix.
Luckily, if you find your car heater not working properly, unlike many systems on the modern motor car, heating systems are more or less built around the same design as they were 20 years ago - which is ultimately a basic one.
That said, there are multiple reasons why your car heater could be busted - and working out which one it is can be tricky.
Equally as frustrating as a car heater not working, is facing problems with your car air conditioning not working properly.
Check our tips and tricks for ensuring that your car air conditioning is working as it should.
If the problem as to why your car heater is not working is simple - and you can diagnose it - then it's possible to fix it yourself.
But some issues are more complex, meaning that to fix the problem with the heating not working in your car, a visit to your local garage is necessary.
For example, a car heater that does not work at all could be suffering from a broken blower motor or switch, while a car heater blowing cold air could be affected by low coolant or a clogged up heater core.
With luck, any issues you have with your car heater not working will become evident in warmer months, so you can fix them before winter sets in.
In most cases, car heater issues fall under two headings:
If you find that your car heater system is blowing air but that your car is not heating up:
If your car heater is not working at all, you're looking at:
In order to fix this, you might have to prise open the heater box, or perhaps even lift a section of the dashboard to access the blower.
Is your car heater blowing cold air instead of hot air?
If you feel the chill of cold air in your car, even after the engine has been running for some time (and the system is set to hot), then the following issues are likely causes as to why the car heater is not blowing hot air:
First of all, check the coolant level - but wait until the engine is completely cool, or you could be burned.
In the case of having sufficient coolant, you can switch on your engine and let it heat up, before checking the temperature at the point where the heater core and hoses connect.
It is best to use an infra-red thermometer to check the car coolant temperature, since it does not require any contact.
If you discover one of the hoses is the same temperature as the coolant but that the other hose is cold, it is likely your heater core has become clogged, which will explain why your car heating is not working as it should.
If your car has a valve in the affected hose, you should check to see if it has got stuck.
Turn off your car heating and listen for the blend door moving.
If you can't hear it move, you may be looking at:
If your car heater is not blowing hot air, then you probably have a faulty blower motor, although there's an outside chance there could be another explanation.
To check the car blower motor you will need some basic diagnostics tools, which will tell you if power is coming through. You will need direct access to the motor to do this.
You might also be facing a faulty blower resistor; relay; or switch.
Each car is different, so how you work out the problem will depend on your model. Check your owner’s manual for more information.
If you believe power is reaching the motor, there are several possible reasons as to why your heater is not working in your car:
In the case that power is going to the motor, you should check the blower fuse, resistor, relay and switch.
If you think the cause for your car heating not working is related to the blower fuse, be sure to replace it with one of the same amperage.
The fuse may have blown due to age, or it may suggest an underlying problem. If the replacement fuse (of the same amperage) does not blow, you may well have identified the problem.
Do not be tempted to replace the fuse with one of a higher amperage to keep it from blowing again.
Most car heater systems - i.e. ones that come with water-cooled engines - harness the coolant to heat the car interior.
The coolant at this point is inappropriately named since it is extremely hot.
This fluid is pushed through the heater core, which is essentially a mini radiator. In turn, air is pushed through the heater core, which results in your cabin being filled with delightfully warm air - or at least, that’s what should happen.
If antifreeze is passing through your heater core there could be dirt or other matter stuck in the heater box, or the blend door is jammed/faulty.
For those without the necessary skills, mechanical aptitude or motivation, and for those who are simply too busy with other things, it may make a lot of sense to let your local garage fix the problem with your car heater, rather than trying to work out for yourself why your car heater isn’t working, and trying to fix yourself.
If your car heater is not working, you may well be wondering if this will cause your vehicle to fail the MOT.
Whilst a broken car heater can be inconvenient (and cold!), it is not one of the core components checked as part of an MOT.
Click here for a full list of car parts checked at an MOT.