There are many reasons for the car heater not working.
The vehicle's heating system is part of its cooling system. Therefore, problems with the cooling system can also result in issues with the heating system.
If your car heating system is not working, the problem can be due to one of only four reasons: problems with the cooling system, issues with the heating core, faulty water pump, or malfunctioning heating blower fan.
Problems with the vehicle's heating system will not prevent you from riding your vehicle in worm days; however, you must get it repaired to be able to drive during cold winter days.
While some causes might be simple and cheap to fix (e.g., thermostat, worn hoses, leaks, etc.), other causes like problems with the water pump might be more complicated and require higher prices to be fixed.
In this article, we will walk you through how the heating system work in your vehicle does, highlight the main causes of a faulty heating system. Finally, we will suggest the necessary repairs by cause to get your heating system working again.
How does the vehicle's heating system work?
To identify the main causes of car heating not working, you need to understand how does the heating system work.
In any vehicle, the heat is generated through the cooling system. When the engine fires, the coolant fluid flows around the engine to reduce its temperature. Then, the heated coolant goes through the radiator to lose the temperature and cool down.
Part of the heated coolant can be circulated the heater core to raise its temperature and therefore, blow hot air to the vehicle. You can control the amount of heat coming to the car using the different switches on the vehicle's dashboard. These switches control the blower fan and the heater valve.
Why is the car heater not working?
The car heater will not work if your vehicle has issues with one of four components:
the cooling system, the heater core, the heater valves, or the blower fan.
Problems with the cooling system
The cooling system can go bad if it has a low coolant level, a malfunctioning thermostat, an existing airlock in the cooling system, deteriorated cooling system hoses, leaking radiator, or faulty water pump.
- Coolant level: heat is transferred to the heating core through the heated coolant fluid. If there is not enough coolant fluid in the system, the required heat needed by the heating core will not be generated. Therefore, the core will not be able to blow hot air to the vehicle.
- Thermostat: the vehicle's thermostat is responsible for adjusting the temperature of the coolant around the engine.
The thermostat works as a valve to prevent the coolant fluid from flowing to the radiator when the engine is not worming enough. When the engine reaches the upper allowed temperature, the thermostat opens and allows the coolant to pass through the radiator and cool down.
If the vehicle had a stuck open thermostat, the coolant fluid would stay cold all the time, and therefore, the heating system will not blow hot air.
- Airlock: sometimes, the coolant fluid might have a big air bubble due to leaks. This air bubble can affect the transfer of temperature from the coolant to the heating core. Therefore, when you switch the heating system on, the required heating temperature might not be achieved.
- Issues with the hoses: like any other vehicle's parts, the cooling system hoses might tear and wear over time, causing the fluid to leak and probably lose some heat to the surroundings.
Issues with hoses are most likely to appear in older cars where hoses feel like sponges indicating an urgent need for replacement.
- A leak in the radiator: in older vehicle's the engine radiator might leak some of the coolant fluid resulting in a low coolant level. As we mentioned before, a low coolant level will not transfer the required heat to the heating core, and therefore, will cause issues with the heating system.
- Problem with the radiator cap: the vehicle's radiator cap is responsible for keeping the appropriate coolant pressure level. If the radiator cap stuck open, there would not be enough pressure in the cooling system. As a result, the coolant will not flow properly around the heating core and, therefore, affect the vehicle's heating capacity.
- Faulty water pump: the water pump is responsible for pumping the coolant fluid and circulates it with the proper power around the engine. If the pump does not provide the optimal power to circulate the coolant, the heat transfer will be disturbed and therefore affecting the performance of the heating system.
Problems with the water pump are considered the most complicated reason for a faulty heating system. Fixing the water pump is one of the most expensive vehicle repairs; however, it only occurs in older vehicles.
- Issues with the engine's fan: Newer vehicles are now equipped with additional engine's fan. This fan is responsible for further cooling down the engine when it gets too hot. A faulty engine fan might run all the time, causing the cooling fluid to stay at a low temperature all the time. Cold coolant fluid will not generate the required heat needed by the heating system, and therefore, your car heating will not work properly.
Problems with the heater core
- Clogged internal passage: the heater core works like a radiator that collects heat from the hot coolant around it, and then transfer it to the air blown to the vehicle.
The heater core might get clogged due to the build-up of contaminants or particles during the usage time. A clogged heater core will prevent the heat from getting into the vehicle's inside.
- Clogged heater core outer fins: on the outside of the heater core, there are small fins that allow air to circulate into the heater core. These fins might get clogged overtime by particles or debris, causing troubles with the car's heating system.
Problems with the blower fan
The blower fan is responsible for blowing the hot air from the heater core to the vehicle's inside. If the fan is not working, then the heating system will not be able to heat the vehicles inside fully.
Problems with the valve
The heater core has a valve to control the transfer of heat from the heating core to the vehicle's cabin. A stuck closed valve can prevent the heat from getting to the car and, therefore, causing the heating system not working properly.
How to repair not working heating system?
Repairing the heating system depends on the cause of the problem.
For example, if the heating system is not working due to issues with the cooling system, you can do one of the followings depending on the faulty part:
- Confirm that there is an appropriate coolant level in the cooling system. If you added the coolant fluid and noticed that the coolant level is not rising enough, this might indicate a leak in the system. In this case, you need to locate the leak source and get it replaced or repaired.
- Check if the problem is due to a faulty thermostat. To do so, change the thermostat from hot to cold and monitor the sound. When you switch the thermostat from hot to cold, you should hear the thermostat blend door moving. If you did not hear this sound, this indicates that the thermostat has an internal problem and might need to be replaced.
- If the issue is due to a faulty thermostat, you need to remove it and install a new one. Installing a new thermostat is a very straightforward easy fix that you can do it yourself to save on labor cost.
- If the problem is due to an air bubble in the coolant fluid, you need to get rid of any air bubbles in the system. To do so, open the cap of the coolant tank, let the engine fire for a couple of minutes, and finally, close the coolant tank cap.
- Heating system problems due to the radiator can be fixed with one of the following: check and repair any radiator leaks, install a new radiator cap if it is not working properly, or install a new radiator in more severe problems.
- If the water pump is not working properly, you need to have it checked by a professional mechanic. The mechanic can decide if it is repairable or if you need to install a new water pump.
- Check if the engine's fan is running only when needed and not running continuously. A faulty engine's fan must be replaced for the heating system to work properly.
- Check if the problem is due to the heater core. You can feel the temperature of the two heater core hoses, and if one of them is colder than the other, then there might be something blocking the hot coolant from entering the heating core.
- Problems with heater core can be fixed by doing one of the followings: flush the heater passage and the exteriors to get rid of any debris or blocking particles, if cleaning did not resolve the issue, you might need to replace the entire heating core
- A damaged or malfunctioning blower fan can be fixed by replacing any blown a fuse or replace the entire fan if needed.
- If the mechanic determined that the heating system problem is due to issues with the heating valve, the valve should be repaired immediately.
Fixing the heating valve depends on the type of valve you have in the vehicle. If you have a manual valve, the mechanic can fix it by replacing the faulty parts. On the other hand, an electronic valve must be diagnosed by an experienced mechanic to determine the exact cause of the problem.
How much does it cost to fix the vehicle's heating system?
As we mentioned before, there is a wide range of causes for the heating system to go bad.
Therefore, it is hard to say a fixed price to get your heating system working again.
The repair price depends on the car make, model and year. In addition, it depends on how severe the problems are and how easy is it to get to the faulty part. For example, replacing a water pump requires a lot of labor cost as it is hard to reach.
In general, most heating problem repairs can be taken care of at about $300 to $1,000.
Can regular maintenance prevent heating system failure?
The short answer is yes. If you have a mechanic, check the heating system during regular maintenance, you might prevent high repair costs for fixing the heating system.
For example, the mechanic can tell you if the coolant level is below the optimum level, which is an indication of some leak in the system.
In general, heating system problems happens only in older vehicles and vehicles with higher mileage (e.g., 60,000 to 100,000). Therefore, it is recommended that if you are driving an older vehicle to maintain regular checking on the coolant fluid level and the other internal components to prevent heating system failure.
Problems with the car heating system will not prevent you from driving during worm days. However, you must get the system repaired if you are driving in freezing winter days.
The heating system can go bad due to issues with one of the following components: cooling system, heating core, engine's blower fan, and heater valve.
Some of the mentioned problems can be easily repaired at lower prices, like replacing a thermostat or worn hoses. On the other hand, some issues might be more complicated and require higher prices to be fixed, like replacing a water pump, for example.
You can fix the heating system by confirming having the required coolant level, fixing any leaks, replacing the faulty fan, heating valve, or radiator.
Despite the cause of the heating problem, you need to get it fixed to avoid higher repairs prices in the future.