Common Car Heater Problems Explained
Car issues can make people scratch their heads. If your car heater is suddenly blowing out cold air instead of heat in the middle of a bitterly cold winter, you have a good reason to be frustrated. Unreliable car heaters can make the cold winter months practically unbearable.
Several things can potentially go wrong with automotive heaters because, much like a home heating system, there are many components working together to heat your car. If one or more of these issues is present, your vehicle may blow out cool air rather than heat:
- Not enough coolant in the engine
- Problems with the heater core
- Clogged or broken heating controls
- Dysfunctional thermostats
Lets take a look at each of these issues more in-depth
How To Fix A Broken Heater
Depending on the problem, the fix can be as simple as refilling the coolant or as complicated as a full-on heater core replacement. Lets go over the most common fixes for automotive heating problems here.
Safety Notice: Working on your car, even on the little things, can get dangerous. To prevent damage to you or your vehicle, always use proper safety precautions. Always wear gloves and protective eye equipment, and always use jack stands when working underneath a lifted car.
Its absolutely possible to complete a full-on repair of your cars heating system at home, but its important to remember that performing repairs like replacing the heating core is both involved and time-consuming. Youll need to make sure that you have the right tools and a solid place to work before diving in to start any heater repairs at home.
Is There Enough Water In The Car
Your heater uses the heat from the coolant circulating around the engine. You should also have antifreeze in your coolant mixture, this not only stops the coolant from freezing inside your engine but also stops it from corroding. The heater is higher up than the rest of the cooling system, and thus last in line for coolant. Thus the first thing you should do, if you have no heat, is to see if there is, in fact, enough coolant in your engine.
You can do this by lifting the bonnet and looking at the header tank, which collects overflow coolant from the radiator. This is a large tank, usually clear plastic, with a conspicuous cap, rubber hoses coming off of it, and “Max” and “Min” markings on it. It is positioned a little higher than the radiator, usually to one side or the other of the engine, directly above a wheel.
If this tank is empty, you can fill it back up with ordinary water you can add some antifreeze if you want. If your header tank is full then proceed to the next step. If you are not certain which is your header tank, ask a friend, or take the car to a local garage.
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How To Fix A Car Heater That Isn’t Blowing Any Air
If the heater isn’t blowing any air, a faulty blower motor or electrical connection might be the problem. Follow these steps to fix it.
Check if the blower motor receives power. The only way to determine which component has failed is to grab some basic diagnostic tools, access the blower motor, and check whether it receives power. The specific diagnostic procedure varies with the vehicle.
If it receives power, check if the blower motor is burned out. After removing the blower, you might find a squirrel cage so clogged with debris that the motor can’t operate. In other cases, a broken wire, rusted connections, or a disconnected pigtail assembly might be the issue.
If the blower doesn’t receive power, check that the blower fuse isn’t blown. A blown fuse often indicates an underlying problem, so never replace one with a larger fuse to prevent it from blowing out again. If you replace a blown fuse with one of the same amperage and it doesn’t go out, the fuse likely failed due to age. If the original fuse is not blown, trace the problem to the source by testing the resistor, relay, and switch.
Why Isnt The Car Heater Blowing Hot Air
Here are the most common reasons why your car heater isnt blowing hot air.
- Low coolant:Whether caused by a leak or water evaporation, low coolant is the most common source of poor heater output.
- Thermostat: A stuck-open thermostat prevents the engine from heating up.
- Heater core: A clogged heater core restricts coolant flow, giving up little or no heat.
- Electric cooling fans: Due to a bad sensor, switch or controller, electric cooling fans running constantly prevent coolant from reaching operating temperature.
- Heater control valve: Some vehicles have a heater control valve that only opens when the temperature control is set to hot. A stuck-closed valve prevents hot coolant from flowing through the heater core.
- Blend doors: An inoperative temperature control, blend door or a failed blend door actuator stuck in the cold position prevents heated air from entering the passenger compartment.
If your vehicle was serviced recently, there could be another reason. If you had the fluids topped off or the radiator flushed with new coolant, or if you have a defective radiator cap, air bubbles could have made their way into your cooling system. Air bubbles keep coolant from circulating through the cooling system, including the heater core.
Heres how to solve the air bubble problem yourself and get your heater working again. Dont laugh: Like a baby, your cooling system needs to be burped.
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Reason #: The Condenser Is Broken
If there doesnt appear to be anything blocking the condenser, its possible that it may be broken altogether. A broken condenser can be caused by a puncture from road debris going through the grill of your car and damaging the part, or equipment failure.
If you notice any noticeable punctures in the condenser upon a visual inspection, typically the only way to fix the issue is through replacement.
Inspect Your Blower Motor
Even if your fuse is working properly, youll want to check out your blower motor, which is usually located underneath the dash on the passenger side.
Test your blower motors connections
- Disconnect the blower motor connector.
- With your key and heater switch both on, test the connector using a test light. Our mechanic shows you how to test the connectors power and ground at 1:28 in the video above.
If your blower motor connectors power and ground are working, that means everything in front of that connector is working, which narrows down the issue to the blower motor itself, and youll need to replace it.
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How To Maintain The Car Heater
If at an outside air temperature is, lets say, -25 degrees C , the heater warms up the cabin up to +16 degrees C from the bottom and +10 degrees C from the top , the heater can be considered quite serviceable. In this case, the temperature in the rear seats of the car should be approximately +15 degrees C . The presence of such a noticeable difference between the temperature at the bottom of the cabin and the temperature at the top will provide a comfortable ride for both the driver and the passengers.
To avoid such problems, it is recommended to carry out all preventive measures on time and carefully. This will allow you to enjoy a ride in a well-warmed car. You will protect the windows from the frozen layer or steam, making your journey safer. The more you drive the car, the more attention its heating system requires. This applies to all vehicles.
Why Did My Heater Stop Working
The most common cause of a failing heater core and heating system, in general, is dirty coolant. Over time, the coolant liquid can become contaminated with particles and dirt from its travels through the engine and cooling system. This can cause the heater core to clog and fail.
Thats just one of the common reasons, so we dig deeper into additional causes of a failed heating system below.
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Why Wont My Car Warm Up
If the temperature gauge isn’t moving much from the lowest reading, or the car runs poorly for more than a few minutes on a cold day, the cooling system may not be working properly. There are a few potential culprits for why your car engine coolant may not be heating up:
- Coolant Level – The first thing to check is the coolant level! If the coolant is low, there may be air in the system, which will lead to localized hot and cold spots. Typically the gauge needs to be in the coolant to read properly.
- Air Lock – If you have had a coolant leak, or have recently drained and filled the system, then you may have air lock. When this happens an air bubble gets trapped in the system preventing the engine coolant from circulating correctly.
- Gauge/Temp Sensor – Is the gauge actually working? Is it reading correctly? Modern cars have an electronic coolant temperature sensor connected to the OBDII computer which informs the temperature gauge. These sensors can fail. Often they will be flagged when you read the OBD fault codes.
- Thermostat – A faulty thermostat can cause too much or to little cooling. If it’s stuck open, the engine is going to take longer to warm up because coolant will circulate all the time. You can remove the thermostat and test it in a pan of almost boiling water, it should open just before it reaches the boiling point, then close as the water cools. If doesn’t move, then replace it!
Reason #: Your Car Is Leaking Refrigerant
A refrigerant leak can occur at any point in the air conditioning process and so its sometimes difficult to pinpoint the exact location of the leak. The most common places where leaks are found are at A/C unit hose connections.
Its sometimes possible to see an oily substance accumulating around these connection, which is likely the source of the leak. You or a technician can use a sealant found at most auto parts stores to close the leak.
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Broken Heater Flaps/blend Door Actuators
There are flaps under your dashboard that regulate either the airflow or the coolant flow through the heating core. If one of these flaps or the electric actuators to them is defective, there is a great risk that your heater will not function as suggested.
If you have a newer car with electric motors for the flaps you will most likely get an error code on them when you scan the system with a diagnostic computer.
You can also locate the flaps and see if they move when you change the heater control. If they do not they are most likely broken. It can be difficult to see them on many car models as they are often hidden very deep down under the dashboard.
It also happens that these actuators lose their programming, and they need to be preset with a diagnostic scanner again.
Air In The Cooling System
Air inside the coolant system is a very bad thing because it can cause overheating of your engine, which can cause severe damages to your engine.
Air can come into the coolant system if the coolant level was once very low or if you replaced any parts in the coolant system recently. In rare cases, it can also come from a bad or leaky head gasket.
Airlocks often get stuck in the heater core inside the car, making the cars heater blow cold air.
To get rid of air in the cooling system, you have to bleed the cars cooling system. The process can be pretty difficult if you do not have the knowledge, so I recommend letting a repair shop do it for you.
If you feel that you are comfortable enough to bleed it, you can follow our guide here: How to Bleed Your Cars Cooling System
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Broken Car Heater: Will It Fail Mot
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 , 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.
Equally as frustrating as a car heater not working, is facing problems with your car air conditioning not working properly.
Reason #: The Condenser Is Blocked
The condenser of your vehicles air conditioning unit is supposed to re-cool hot refrigerant once it has been compressed. This is done using the airflow that comes through the front of your car as you drive. If the condenser is blocked by some type of debris from the road, then it will be unable to properly cool the refrigerant and your cars system will continue to operate with overheated refrigerant. This will quickly cause the A/C unit to only expel hot air.
In most vehicles, the condenser is found at the front of the car, so it should be easy to visually see if anything is blocking it. This can easily be removed from the grill of your car and the issue should be resolved.
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Your Ac Is Leaking Refrigerant
Its actually very easy to find if your AC is leaking refrigerant.
Cost Of Repair
Repair It Yourself
In the best scenario, you can use a commercial product to stop the leaking. These products say that they will fix leaks in condensers, evaporators, hoses, and gaskets. The products go for around $25. If this doesnt work, take your car to the mechanic.
Faulty Car Ac Compressor
This is a component that you dont want to fail. Not only will it disable your AC, but it will bring you a huge invoice to pay. This is the most important component of a car AC system. When it starts to fail, it will show a couple of warning signs:
Cost Of Repair
Like I said before, this is not something that you want to fix. It is very expensive.
The compressor can cost from $509-$3188. The labor is anywhere from $322-$805. You can save up some money by fixing it yourself. Make sure you have the required tools before starting your work.
Repair It Yourself
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Why Is My Car Overheating And No Heat Coming From My Heater
When I went to start my car this morning, I immediately noticed that the interior heat was blowing cold. I sat there with the engine running, waiting for it to warm upâbut it never did. After a few minutes, I also noticed that the engine temperature was rising rapidly. Which doesnât make sense since itâs freezing outside. What would cause the engine to overheat but the heater to blow cold air?
itâs not uncommon for your car to overheat and have no heat coming from your heaterproblem with your coolant system
- Not enough coolant
- Faulty heater core bypass valve and/or hoses
- A blockage in the heater core
You should never drive your car when it is showing signs of overheating
Common Car Heater Problems
In90% of the cases, car heater problems are the result of one of the following reasons:
- The heater switching system might be faulty.
- The cabin air filter might be choked, restricting the airflow through the heater core.
- The thermostat valve might not be working right.
- The heater core might be clogged.
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How Can We Help
Just because your car air conditioner has stopped cooling doesnt mean that all is lost. In fact, the fix may be a relatively inexpensive repair that can be done in just a matter of minutes. We understand that this can be an extremely frustrating thing to happen to your vehicle, so we wanted to equip you with the necessary knowledge to troubleshoot these things on your own if possible.
If youre still having trouble trying to fix these issues yourself though, and youre in the Central Missouri area, then feel free to give us a call or stop by our repair shop. Wed be happy to have our experienced ASE-certified technicians take a look and get you back on the road in no time.