Car Heater Only Works When Driving? 5 Interesting Reasons!

Why does your car heater only works when driving? The following issues are to blame: low coolant, malfunctioning thermostat, the system’s air, faulty heater valve, blocked heater core, and radiator leak.

Any of these reasons can cause you to stop your car in the middle of a cold day. The goal is to stay warm as you learn the cause of your heater not working when driving.

Why does your car heater only works when driving

The car heater working when going is still inconvenient and uncomfortable. It might become very hazardous depending on how cold the weather can be. Learn the basics of how the vehicle’s heating system works. This way, you will locate what exactly is causing this to occur. So, learn more detailed explanations to this problem.


Reasons Why Car Heater Works When Driving

Below are the complete reasons why a car heater works when driving.


#1. Malfunctioning thermostat

The system’s thermostat that malfunctions and stays open causes a car heater not to work as you stop the car. The job of the thermostat is to sift the radiator’s coolant. If it gets stuck open, it will not do its job correctly. The malfunction brings up the device’s issues. Fix the stuck and available thermostat that needs replacement soon. Ensure to cool the car first and find the thermostat in the radiator’s foundation. Place the bucket below a radiator hose as you detach it. Replace the damaged thermostat with a new one. Next, place the hose again on and above the coolant as needed. Ensure air is inside the system as it can bring issues along the way.


#2. Flawed heater valve

A faulty heater valve is another cause of a car heater only works when driving. It works to permit the coolant into a heating core rather than a radiator. Diagnose the issue as you run the car for around ten minutes while the heat is on. Search for the valve of the heater next to the firewall at the back of the engine. Get near the hoses on any of the valve’s sides. A hot engine and its side hose and an excellent hose mean a faulty heater valve. So, fix the heater valve after figuring out the vacuum and cable. Figure out how to operate it, allowing testing its heating valve. Adjust the heater valve manually using an electronic or vacuum method.


#3. Low coolant

The coolant regulates the temperature of the engine and the flow of hot air as it reaches the cabin. The engine builds up a lot of heat while working; the coolant collects the heat generated as transported to the vehicle radiator to cool it completely. A low coolant and a heater turned on led you to notice the car heater works when driving. The coolant system properly functioning is crucial to many components in the vehicle. The heat does not present while the vehicle is idle is a sign something is troubling. So, check for a possible problem with the coolant level.

Take caution and do not open a pressurized cooling, or cause personal injury. Check the manual to see how you will review the coolant levels. Better yet, hire a professional to check the plan for you. There are still more reasons why the coolant levels are low, like the leaks and periodic maintenance of the system.


#4. Heater core blocked

Please search for the core of the heater at the back of the dashboard with some issues as it is tiny. The little holes are blocked reasonably by the old coolant, small debris, and dirt. Test the heater core by enabling it to go idle for ten minutes while the heat is on. Test the hoses carefully on a firewall at the back of the engine. You may experience some blockage if they don’t get warm enough. The right thing to do is unclog the heater core after fixing the jam. Use some flushing agent that is an especially-made cleaner. It safely enters the cooling system to clear the blockages.


#5. Radiator leak

A leak in the radiator causes the car to lose its coolant, as this causes heater problems like adverse effects and air blocking often connected with the low coolant. Find the leak and search for some coolant leakage in the radiator, as this is where you see the hoses connect. Fix the problem depending on the origin of the leak. Get some replacement or hire a mechanic to see the damage or fix the source of the radiator issue. But a simple fix will do if the problem comes from the hose end. Tighten the clamp as you hold the hose on to resolve the problem. You may also want to read about car heaters not blowing hot air.


It’s A Wrap!

Now you learn the reasons why a car heater only works when driving. And there are many possible reasons why this occurs in the first place. The important thing is that you stop your car first and know which causes: radiator leak, blocked heater core, faulty heater valve, and malfunctioning thermostat is the real cause of the problem. If you cannot fix the problem, hire a maintenance specialist to help you. You may want to read related articles; know why is my car heater not working and how to make the car heater warm up faster.

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