Heaters are present in cars to maintain the internal temperature. Overheating in cars and malfunctioning of heaters is the worst situation on cold days.
Car overheating and heater does not work due to low levels of coolants, contamination of coolants, leakage of coolants, clogged heater cores, and faulty radiator. In addition, the issues also come due to bad blower fans, failure of blend doors, air bubbles in the cooling system, failure of thermostat, and stuck heater control valve.
Fixing the overheating issue of engines is necessary because it can ruin your cars. Moreover, check the heater’s working and inspect the problem in them to fix it. It is challenging to drive the vehicle when blower fans are blowing cold air instead of warm.
| Car overheating and heater not working | Solutions |
| Coolant problems | Check coolant levels and contamination in them |
| Bad blower fans | Replace blown-out fuse and burnt-out motor |
| Failure of blend doors or heater control valve | Change the blend door actuator and valve |
| Faulty radiator | Seal the cap carefully |
| Air bubbles in the cooling system | Refill the coolant |
| Faulty thermostat and issue with button | Remove the contaminants from thermostat and replace button |
| Clogged heater core | Flush the outer inlet with water to unclog dust and grime |
| Failure of cooling fan relay | Identify issues using scanner tools |
Coolant problems
Coolant is the liquid material moved in cylindrical blocks to absorb heat from the engine. It dissipates the heat from the engine block and protects from overheating issues.
The hot coolant moves through the heater core before moving back to the engine. It supports the functioning of the heaters in your vehicle.
Sometimes the blower fans stop blowing hot air in winter because of low coolant levels. As a result, the heat accumulates in the engine compartment and causes overheating.
The contamination in coolant and disturbance in the ratio of antifreeze and water cause them to freeze in winter.
The frozen liquid cannot move through coils and produce enough warm air. Moreover, leakage of the coolant due to the damaged system also causes the issue.
Leakage occurs due to a damaged radiator cape, hose, and blown-out head gaskets. You can fix it by checking the coolant level in the radiator.
In addition, check the leakage through the radiator cap and replace them. It is also necessary to change the broken head gaskets with new ones.
Bad blower fans
The blower fans blow warm air when coolant passes through the heater core. Sometimes these fans become faulty and cannot receive the hot air from the dashboard vents.
The faulty blower fans also cause fogging up on the windows and windshields in winter because of temperature differences.
The blower fans become faulty because of their damaged internal components. These components also become bad due to malfunctioning of the electric system.
The blown-out fuse of the blower motors inhibits its functioning. Moreover, you cannot receive warm air due to problems with the fan motor and damaged wirings.
Check the motor of the blower fans; sometimes, the burnt-out motors do not get current from the power source.
The burnt-out motors seem darker in color, and you can also feel a burning smell from there. So replace the burn-out motor with a new one.
Failure of blend doors or heater control valve
Blend doors are located on the backside of the dashboard in your cars. These help control the intensity of the air and temperature.
These work with the climate control system of the vehicle. The doors allow the entry of warm air when you turn on the heater and also blow out cold air when you turn on ac.
Sometimes these doors get stuck in one position, and you cannot change them. You cannot receive warm air from the heaters when these doors get stuck in the cold position.
The blend doors also break due to their age and frequent position changes. The blend doors contain actuators that are responsible for their opening and closing.
You can fix the issue by inspecting the HVAC system and replacing the blend doors actuators if these are faulty.
Moreover, you have to change these doors if they are not working and get stuck in one position.
Faulty radiator
A radiator is a container-like structure made of rubber material to store the coolant or antifreeze. Coolant from the radiator cannot reach the heater core when there is leakage in this system.
You cannot receive hot air from the air vents when there is not enough antifreeze to warm the air. The leakage in the radiator comes due to its age.
The leakage also occurs due to damaged caps and seals. Moreover, these also get contaminated and start to lose their strength.
You have to change them after every 3 to 5 years to reduce the risk of damages. Check the texture of the hose and replace it if it is soft and pliable instead of hard and firm. Check the corrosion in the tubes of the radiator and clean them.
Air bubbles in the cooling system
Air bubbles in the cooling system also cause an issue in the movement of coolant in the engine and to the heater core, which can cause overheating and malfunctioning heaters.
The air bubble is the small pockets of the cooling system’s coils. The air bubbles formation occurs when you refill the coolant.
Poor sealing of the radiator hose and blown-out head gaskets sends air into the system. Moreover, the failure of the water pump and reservoir leakage also cause this issue.
You can fix the issue by properly sealing the radiator cap. Then, carefully refill the coolant with proper flushing and check for leaky head gaskets.
Faulty thermostat and issue with button
The thermostat is the sensor-like component that controls the coolant’s flow according to the engine’s temperature.
These become faulty due to their age and contaminated coolant. In addition, the coolant cannot reach the heater core because thermostats become faulty and cannot sense the temperature change.
Moreover, the heaters stop working in your car because of the faulty buttons. These buttons cannot transfer the signals to the heater control valve to transfer the coolant from the radiator to the heater core.
You can fix it by checking the connection of the buttons. In addition, you can reduce thermostat-related issues by changing the coolant.
Mix the anticorrosive agents in the coolant so it cannot deteriorate the thermostat and affect its functioning.
Clogged heater core
The heater core also works as the radiator, and hot coolant moves through them to warm the air on the passenger side.
The heater coil is the set of tubes that is present under the dashboard to warm the air and then blow this air through air vents.
Heaters cannot work in your car when there is an issue with the functioning of the heater core. The clogging of the tubes occurs due to the use of contaminated coolant.
The leakage also occurs in tubes; you can see the greenish fluid with a fruity smell under the dashboard.
You can fix the issue by flushing out the heater core with water. Water flush helps remove the dust and grime from their coils.
You have to connect the water hose with an outside inlet to flush the water.
Failure of cooling fan relay
The cooling fan relay is the engine fan switch responsible for turning them on and off. These work with the electronic control module of the vehicle.
The ECU system turns on the cooling fan relay when the temperature in the engine compartment is high to blow the cold air and maintain the internal conditions.
Sometimes these switches become bad and cannot turn on the fan, leading to overheating in the engine.
The frequent switching on and off of the relay also turns off the thermostat. You can fix the issue by checking the ECU system with scanner tools.
You can see the fault codes on the screen of the scanner tools, and you can easily resolve the problem.
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