In winter, it is very hard to drive when your car heater blowing cold air.
Problems with the vehicle’s heating system can be either heater blowing cold air or coolant is not flowing through the heater core. In this article, we will focus on heating system problems that cause the heater to blow cold air.
For a heating system to work properly, your car must have the appropriate coolant level in the engine, a perfectly working thermostat, a cooling system without leaks, and a working heater core.
If your vehicle has any problem with any of the mentioned components, you will have a car heater blowing cold air.
In this article, we will walk you through how the heating system work in your vehicle, the main causes, and solutions for a car heater blowing cold air. We will also highlight the average repair cost for each cause.
Where does the heating system heat come from?
There are three types of heating systems in the automobile world. Heating that is part of water-coolant engines, heating that is part of air-coolant engines, and finally heating that is part of electrical engines.
Since most modern vehicles operate on water-coolant engines, we will focus this article on heating systems in water-coolant-engine vehicles.
The basic principle of how heat is generated in most vehicles is very simple. When the engine warms up, the coolant around it absorbs some heat and increases its temperature. The heated coolant then goes through a special valve (i.e., the thermostat) to reach the radiator, which reduces its temperature.
For the heating system, part of the heated coolant passes through a small radiator-like component called the “heater core.” The heat is then transferred to the vehicle’s internal through a blowing fan.
It is not surprising for the heating system to take time until it starts blowing warm air to the vehicle as it takes some time for the engine to warm up and, therefore, increase the temperature of the coolant fluid.
What are the causes of a car heater blowing cold air?
While there is a wide range of causes for a heating engine to go bad, knowing that the system is blowing cold air shortens the list of expected causes. In this section, we identify the main causes of a heating system blowing cold air and what you can do about it.
Problems with the engine’s thermostat
The thermostat works as a valve to control the coolant flow to the radiator. When you start the engine, the thermostat remains closed and does not allow the coolant to flow to the radiator. Once the engine reaches the upper allowed temperature, the thermostat opens and allows the coolant to flow to the radiator to be cooled down.
A bad thermostat might be stuck opened or stuck closed. If the thermostat stuck closed, the coolant engine will be overheated and self-destructed in a very fast time. In this case, there will be no hot coolant running through the heating core, and therefore, your heating system will only blow cold air.
On the other hand, if the thermostat is stuck open, the coolant will run through the thermostat continuously. In this case, the coolant will be cold all the time, and all the coolant running through the heating core will be cold as well. Therefore, the heating system will only blow cold air.
Solution: if you determined that the problem in your heating system is due to a faulty thermostat, then in most cases, you need to install a new thermostat.
Installing a thermostat is a very straightforward task. Follow the following steps to replace the vehicle’s thermostat
- Ensure that the vehicle is fixed in place.
- Give some time for the vehicle to cool down.
- Locate the thermostat housing. It is located at the end of the upper house for the radiator towards the engine.
- Unbolt the two large bolts holding the thermostat housing in place.
- Remove the faulty thermostat and install the new one. Make sure to install it in the correct direction.
- Close the thermostat housing and secure it tightly with the two large bolts
- Give the vehicle a test drive and try the heating system.
Cost: replacing a thermostat is one of the repairs that depends heavily on the labor cost—usually, the thermostat costs from $30 to $60 on parts. However, the labor cost can range from $90 to $100. If you decided to replace your thermostat by yourself, you would save a great portion of the repair cost.
Low coolant level
The coolant fluid is the source of heat supporting the heating system. If there is not enough coolant in the system, the heating system will not receive the required amount of heat needed to blow hot air to the vehicle’s internal.
In general, a very low coolant level indicates some fluid leaks that could be due to problems with the hoses, connections, radiator, and other components of the cooling and heating systems.
Solution: if you confirmed that the heating system issue is happening due to a low coolant level, you need to top up the coolant.
Add coolant fluid to the appropriate level according to your vehicle’s owner’s manual. If you see that the coolant level is dropping, this is a clear indication of a fluid leak.
In this case, you don’t want to wait a long time to avoid further damages to your engine. Take the vehicle to an expert mechanic, have him check the locations of the leaks, and then replace the deteriorated parts.
Cost: coolant change or filling is usually done along with other bigger repairs. In general, a coolant change cost can range from $160 to $200 without labor cost. Labor costs can vary depending on the location where you get it changed.
If the issue in the heating system is due to a coolant leak, then the price can increase significantly. On average, expect to pay about $800 to fix any coolant leaks in your system. If you were able to locate the leak in the cooling system, you can fix it on your own and save tons of labor cost money.
Air bubbles in the cooling system
The heating system can also blow cold air if there are big air bubbles in the coolant fluid. If the coolant has air bubbles, the heat will not be transferred appropriately to the coolant. As a result, the coolant running through the heating core will be cold, resulting in cold air blowing through your heat system.
Solution: to get rid of any air bubbles in the coolant fluid, you need to follow the followings steps:
- Set the heating system to the maximum level
- Open the coolant tank by removing the cap
- Top up the tank with more coolant till it reaches the optimum level
- Fire the engine while the tank cap is still open
- Let the engine idle for a couple of minutes
- Add more coolant if the coolant level dropped once the thermostat opens
- At this point, any air bubble should leave the coolant fluid through the tank opening
- Once the engine is warmed up, close the coolant tank and test the heating system.
Cost: removing air bubbles from the cooling system does not cost any money if you do it on your own. It does not involve any new parts installed, and it does not require any specific mechanical skills. Therefore, it is recommended that you do it on your own to avoid additional payments to the auto repair shop.
Issues with the heater core
Another reason for car heater blowing cold air is a clogged heater core. The heater core has a narrow internal passage. This passage might be clogged with particles that buildup during the period of usage.
Besides, the heater core has some fins in the external that can also be clogged due to debris or other particles coming from outside.
A clogged heater core will prevent the coolant from running through it. As a result, the heater core will remain cold all the time, and therefore, causes the heating system to blow cold air all the time.
Solution: a clogged heater core passage can be cleaned by flushing it. A clogged heater core exterior can be cleaned by manually removing any debris or particles clogging it. If flushing the heater core passage or cleaning the heater core exterior did not solve the heating system problem, you might need to install a new heating core.
Cost: if you determined that the problem in your heating system is coming from a clogged heater core, expect to pay from $80 to $90 for flushing the system.
On the other hand, if the mechanic decided that you need to replace the entire heater core, the price can get much higher depending on the vehicle’s make, model, and year.
Replacing a heater core does not cost a lot on parts, on average, expect to pay between $80 and $250. However, the labor cost is expected to be very high due to the complicated work need to replace the heater core. The labor cost can get significantly higher when getting it replaced at a dealership as compared to an auto shop.
Issues with the heater controls
Sometimes the problem with heating system blowing cold air is not due to any significant internal issues. The problem can simply be due to the heating controls
Over time of use, the heating control buttons might get stuck, clogged, or broken, resulting in a hard time controlling the heating system.
Solution: clogged or stuck heating system controls and buttons need to be replaced with new ones.
Cost: replacing the vehicle’s heat switch buttons depends on the vehicle’s make, model, and made. For example, expect to pay $60 for replacing a 2008 Toyota Tundra or a 2014 Ford Escape. However, a Chevrolet Cobalt switch button replacement can get up to $300 on parts only.
Jammed Blend door
The blend door in the heating system is responsible for allowing the air to move from the heating system to the vehicle internal. If the blend door got stuck or jammed, air would bypass the heater core, and only cold air will be blown out of the heating system.
Solution: like the heater control buttons, you need to get the blend door replaced.
Cost: on average, you should expect to pay between $460 to $ 550 on parts only, to replace the blend door. Labor cost can get as high as $500 if you get it fixed at a dealership. Usually, a jammed blend door is fixed as part of other bigger repairs like water pump replacement, hood support strut replacement, blower motor resistor replacements, and others.
If your heating system is blowing cold air, you will experience a very rough winter, and sometimes you will not be able to drive your vehicle.
Problems with the vehicle’s heating system can be either no air or only cold air coming out of the heating system.
A car heating system blowing cold air can be due to a faulty thermostat, low coolant fluid level, malfunctioning heater core, a leaking cooling system, or problems with heating controls and blend door.
Some of the issues causing a heater to blow cold air can be simply fixed, and you can do it by yourself (e.g., replacing a thermostat, filling coolant). Other problems must be repaired at an auto repair shop (e.g., fixing cooling system leaks, replacing the heating core.)
While you can still drive with a faulty heating system, cold air blowing out of the heater can be an indication of complicated problems that might result in engine failure. For example, if the problem in your heat system is due to a stuck closed thermostat, expect a fast engine is overheating and, therefore, engine self-destruction.
Despite the cause of the heating system issue, you must get the heating working if you need to have comfortable driving in winter, and to avoid high repair costs shortly.